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Seafloor organisms are vital for healthy marine ecosystems, contributing to elemental cycling, benthic remineralization, and ultimately sequestration of carbon. Deep-sea life is primarily reliant on the export flux of particulate organic carbon from the surface ocean for food, but most ocean biogeochemistry models predict global decreases in export flux resulting from 21st century anthropogenically induced warming. Here we show that decadal-to-century scale changes in carbon export associated with climate change lead to an estimated 5.2% decrease in future (2091-2100) global open ocean benthic biomass under RCP8.5 (reduction of 5.2 Mt C) compared with contemporary conditions (2006-2015). Our projections use multi-model mean export flux estimates from eight fully coupled earth system models, which contributed to the Coupled Model Intercomparison Project Phase 5, that have been forced by high and low representative concentration pathways (RCP8.5 and 4.5, respectively). These export flux estimates are used in conjunction with published empirical relationships to predict changes in benthic biomass. The polar oceans and some upwelling areas may experience increases in benthic biomass, but most other regions show decreases, with up to 38% reductions in parts of the northeast Atlantic. Our analysis projects a future ocean with smaller sized infaunal benthos, potentially reducing energy transfer rates though benthic multicellular food webs. More than 80% of potential deep-water biodiversity hotspots known around the world, including canyons, seamounts, and cold-water coral reefs, are projected to experience negative changes in biomass. These major reductions in biomass may lead to widespread change in benthic ecosystems and the functions and services they provide., (© 2013 The Authors Global Change Biology Published by John Wiley & Sons Ltd.)

Most small-scale inland fisheries in the Global South prohibit fishing gear with smaller meshes than is legally permitted. Nonetheless, in most instances, this is not strictly enforced. But starting in 2017, Uganda and Tanzania ramped up enforcement on Lake Victoria. We used time series hydro-acoustic data to determine whether the strict enforcement achieved the management goal of increased biomass (t) of commercial species and an increase in the biomass of big Nile perch (> 50 cm). The biomass for 2018–2021 (under strict enforcement) was expected to be greater than in 2007–2017 (prior to strict enforcement). The biomass of key species fluctuated annually, but no spatial or temporal differences in biomass associated with strict enforcement were evident. Similarly, the biomass of big Nile perch did not increase. Our findings suggest that mesh sizes may have limited influence on fish biomass dynamics in Lake Victoria, and that high primary productivity of the lake, high turnover rates of fish species, and limited compliance by fishers likely counteract the effects of high fishing effort on biomass and size structure of fish. Therefore, the high cost of strict top-down enforcement and the societal cost of lost lives, jobs, and livelihoods may not be justified. [ABSTRACT FROM AUTHOR]

Plankton size structure is crucial for understanding marine ecosystem dynamics and the associated biogeochemical processes. A fixation step by acid Lugol's solution has been commonly employed to preserve plankton samples in the field. However, the acid Lugol's solution can bias the estimation of size structure and the preserved plankton size structure can vary with time. Here, we explore the impact of sample storage time on the size-structure of the plankton community preserved by Lugol's solution. Two short-term experiments and one long-term experiment were conducted to explore the change of plankton community size structure with the storage time: covering from a week to a month, and to nearly seven months based on particle-size data obtained by continuous Flow Cytometer and Microscope (FlowCAM) measurements. We found a linear change of plankton size with the storage time in short-term periods (less than 3 months) with a decrease of the slope but an increase of the intercept for the normalized biomass size spectrum (NBSS). However, there were opposite trends for NBSS with increasing slope but decreasing intercept after 3 months. The potential causes of the distinct patterns of the NBSS parameters are addressed in terms of the interplay between particle aggregation and fragmentation. We found large changes in plankton biovolume and abundance among different size classes, which may indicate a distinct effect of acid Lugol's solution on various plankton size classes. The mechanism driving temporal change in the size-structure of the Lugol-fixed plankton community was further discussed in terms of particle aggregation and fragmentation. Finally, we emphasize that the effect of storage time should be taken into account when interpreting or comparing data of plankton community acquired from samples with various storage durations. [ABSTRACT FROM AUTHOR]

Size and sex structure of estuarine-freshwater mysid Neomysis awatschensis in the northern Amur Bay is considered, time of their aggregations formation is determined, and their biomass is estimated on the data of surveys conducted in 2014–2019. The samples were collected at the depth of 0.5–2.0 m in the daytime in May-July. The catches were recalculated per 1 m3 of water. All collected mysids (2212 ind.) were measured under binocular microscope with accuracy of 0.1 mm, weighted by torsion scales with accuracy of 1 mg, and separated to males, females and juveniles. The females were differentiated by 5 stages of their development: 1) immature females with oostegetic rudiments; 2) oviparous females; 3) females with embryos in the marsupia bags without stalk-eyes with black pigment; 4) females with embryos in marsupia bags with black eyes; 5) spawned females with empty marsupii. Time and duration of N. awatschensis aggregating changed by years in dependence on hydrological and weather conditions; the aggregations were either monospecific or mixed with another mysid species — N. mirabilis. The maximum mysid biomass could exceed 500 g/m3 that was appropriate for commercial fishery. The maximum body length of mysid females was 13.7 mm, of males — 12.0 mm. The average length varied from 6.7 to 10.3 mm, being shorter in summer months than in May. Portion of males in the aggregations was always significant (16.3–50.7 %), portion of females varied from 8.7 to 52.5 %, portion of juveniles was the largest in June (29.9–75.0 %). The females to males ratio was 1 : 1 in May and July of 2014–2017, but males prevailed in June 2015 (1.0 : 1.9), whereas females prevailed in June 2016 (1.8 : 1.0). Spawning of the mysids was the most intensive in May-June, though females had embryos at different stages of development in all samples that indicated an extended period of reproduction.

Settlements of bivalve Mya uzenensis are investigated in four littoral areas of the Tauiskaya Guba Bay with different environments. Their density varied from 20 to 194 ind./m2 (518–9680 g/m2) depending on habitat. On suitable soils, the settlements occupied 25–40 % of the littoral zone; the mollusks were distributed mostly in mosaic spots with size 0.5–5.0 m2. Stable settlements in the areas with favorable environmental conditions in the Ola estuary and Vesyolaya Bay were formed by mollusks with shell size of 22.1–91.1 mm and age of 2–14 years. Allometry of the shells growth increased with age until 10 years, then leveled. The stocks of mollusk were assessed for certain areas that allowed to recommend for annual landing 158.4 t of M. uzenensis (7 % of commercial stock).

To explore the effects of coastal eutrophication and warming on phytoplankton biomass and cell size, we analyzed current and historical data for size-fractionated chlorophyll a (chla) in Xiangshan Bay, China. Results showed that micro- and nanophytoplankton overwhelmingly dominated (>84%) in all seasons. The contribution of micro-chla was significantly lower in warm than in cold seasons, whereas contribution of pico-chla showed the opposite result. Overall, the micro-chla contribution increased with decreasing pico-chla contribution from the stable, clear, eutrophic upper bay to the turbulent, turbid lower bay, indicating that phytoplankton size structure on a spatial scale was largely shaped by water column stability and light rather than by nutrients. Since the 1980s, phytoplankton biomass, primary productivity, and micro-chla contribution in Xiangshan Bay have increased sharply with increasing nutrient amounts and temperature. Additionally, it seems that algal bloom seasonality has shifted forward from spring to winter since the power plant operations in 2006. Unlabelled Image • Micro- and nano-sized fractions overwhelmingly dominated phytoplankton community. • Large-celled phytoplankton tended to predominate in well-mixed water column. • Microphytoplankton dominance has increased under eutrophication and warming. • Phytoplankton biomass and primary productivity have increased sharply since the 1980s. • Algal bloom seasonality has shifted forward because of thermal discharge. [ABSTRACT FROM AUTHOR]

Sustainable yields that are at least 80% of the maximum sustainable yield are sometimes referred to as "pretty good yields" (PGY). The range of PGY harvesting strategies is generally broad and thus leaves room to account for additional objectives besides high yield. Here, we analyze stage-dependent harvesting strategies that realize PGY with conservation as a second objective. We show that (1) PGY harvesting strategies can give large conservation benefits and (2) equal harvesting rates of juveniles and adults is often a good strategy. These conclusions are based on trade-off curves between yield and four measures of conservation that form in two established population models, one age-structured model and one stage-structured model, when considering different harvesting rates of juveniles and adults. These conclusions hold for a broad range of parameter settings, although our investigation of robustness also reveals that (3) predictions of the age-structured model are more sensitive to variations in parameter values than those of the stage-structured model. Finally, we find that (4) measures of stability that are often quite difficult to assess in the field (e.g., basic reproduction ratio and resilience) are systematically negatively correlated with impacts on biomass and size structure, so that these later quantities can provide integrative signals to detect possible collapses. [ABSTRACT FROM AUTHOR]

Abstract Long-term studies demonstrated that temperature increases of 3–6 °C above natural levels caused reduction in zooplankton biomass. We hypothesized that large-bodied species would respond more strongly to temperature increases than small-bodied species because they are less adapted to high temperatures. Studies were conducted in three similar stratified meso-eutrophic lakes with different thermal regimes. Enhanced temperature, migrations, food abundance and dissolved oxygen concentrations were analyzed as potential factors that could affect zooplankton biomass. The warmest lake differed from the other lakes by lower total biomass of zooplankton less abundance of large-bodied zooplankton species, smaller population body sizes of abundant cladoceran species and higher food concentrations. Day and night abundances of zooplankton did not differ between the vertical strata and between the pelagic and littoral zones in the three study lakes suggesting that zooplankton did not vertical or horizontal migrations. We suggest that decreases of dissolved oxygen below the epilimnion prevented zooplankton from vertically migrating. As a result, zooplankton accumulated in the epilimnion where temperatures were higher than in the lower strata. Regression analysis showed that temperature had a significant negative impact on the total biomass of zooplankton in the epilimnion of the warmest study lake. Therefore, our results are in accordance with the ecological Bergmann's and James' rules dealing with the temperature-size relationships. [ABSTRACT FROM AUTHOR]

This work aimed to analyse the main characteristics of the bathymetric and geographic distribution, population size structure and size at maturity of the continental slope caridean shrimps Pasiphaea sivado and Pasiphaea multidentata in the western Mediterranean, as well as to try to relate the patterns obtained with geomorphologic and hydrographic characteristics. The study area encompassed the Mediterranean coast of the Iberian Peninsula. In both species, marked differences in depth distribution, density, and population size structure were found between Algerian basin populations, particularly in the Alboran Sea, and those in the Catalano-Balearic basin. Both shrimps showed a shallower bathymetric range in the westernmost region of the Algerian basin than in the rest of geographic sectors, linked to the occurrence of upwelling areas on the northwestern edges of the Alboran Sea. Populations of P. sivado reached larger densities, sizes and maturity size in the Algerian basin. No recruitment of P. multidentata was detected in the Algerian basin, whereas it was present in the Catalano-Balearic basin. In both species, the window range of bottom temperature and salinity was larger in juveniles than in adults. These different distribution and population dynamics imply that ecological functioning of these species differs between the two geomorphological basins of the western Mediterranean Sea.

Current state of the scallop Mizuhopecten yessoensis settlements in Peter the Great Bay (Japan Sea) is considered on the data of diving surveys conducted by RV Ubezhdenny in the coastal zone of Primorye with the depth up to 20 m in summer and fall seasons of 2000-2012. The materials were collected from 11,000 diving stations using standard methods. Total abundance and biomass of the species is assessed by the method of Voronoy diagram (similar to the method of Tissen polygons). At present, total number of the scallop is about 4 million individuals which occupy the area 50 km2. Non-commercial scallops prevail in the settlements of closed and semi-open bays, but the size groups of commercial value dominate in the settlements located in the open waters. For the whole surveyed area, the portion of scallops with the shell height < 100 mm is 29.7 %, 100-120 mm - 20.8 %, > 120 mm - 49.5 %.

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Peatlands cover 3% of the earth’s land surface but contain 30% of the world’s soil carbon pool. Microbial communities constitute a crucial detrital food web for nutrient and carbon cycling in peatlands. Heterotrophic protozoans are considered top predators in the microbial food web; however, they are not yet well understood. In this study, we investigated seasonal dynamics in the community and the trophic structure of testate amoebae in four peatlands. Testate amoebae density and biomass in August were significantly higher than those in May and October. The highest density, 6.7 × 10 4 individual g −1 dry moss, was recorded in August 2014. The highest biomass, 7.7 × 10 2  μg C g −1 dry moss, was recorded in August 2013. Redundancy analyses showed that water-table depth was the most important factor, explaining over one third of the variance in fauna communities in all sampled seasons. High trophic position taxa dominated testate amoebae communities. The Shannon diversity index and community size structure index declined from August to October in 2013 and from May to October in 2014. These seasonal patterns of testate amoebae indicated the seasonal variations of the peatlands’ microbial food web and are possibly related to the seasonal carbon dynamics in Northeast Chinese peatlands. [ABSTRACT FROM AUTHOR]

The three-component model of Brewin et al. (2010) computes fractional contributions of three phytoplankton size classes (micro- (> 20 μm), nano- (2–20 μm), picophytoplankton (< 2 μm)) to the overall chlorophyll a concentration (Chla). Using in situ pigment data, model coefficients were adjusted for application to the southern African marine region. The refined model was applied to seasonal and monthly climatologies of MODIS Aqua Chla around Southern Africa. Chla > 1 mg m − 3 was limited to shelf regions along the coasts of Southern Africa and Madagascar, while values < 0.1 mg − 3 were found over most of the open ocean between the equator and 38°S during austral summer and autumn. In winter and spring, low values (< 0.1 mg m − 3 ) were restricted to smaller regions within subtropical gyres, while values up to 0.7 mg m − 3 extended over a much greater area of the open ocean. Shelf regions in the northern (NB) and southern Benguela (SB), Agulhas Bank (AB), Agulhas region (AR), and Mozambique Channel (MC) all showed similar seasonal cycles of size structure. On average, microphytoplankton comprised > 50% of the total Chla in these regions with little change throughout the year. The AR shelf differed, with picophytoplankton dominating in summer, and micro- and nanophytoplankton the rest of the year. In the open ocean domains of the NB, SB, and AB regions, nanophytoplankton dominated for most of the year, with picophytoplankton being more prevalent during summer and autumn. In contrast, in the AR open ocean, nanophytoplankton were dominant only during winter and early spring, whereas picophytoplankton dominated throughout the year in the MC open ocean. The refined model characterised previously unknown spatial and temporal changes in size structure in various ecosystems around Southern Africa. [ABSTRACT FROM AUTHOR]

Many methods exist to assess the fishing status of data-limited stocks; however, little is known about the accuracy or the uncertainty of such assessments. Here we evaluate a new size-based data-limited stock assessment method by applying it to well-assessed, data-rich fish stocks treated as data-limited. Particular emphasis is put on providing uncertainty estimates of the data-limited assessment. We assess four cod stocks in the North-East Atlantic and compare our estimates of stock status (F/Fmsy) with the official assessments. The estimated stock status of all four cod stocks followed the established stock assessments remarkably well and the official assessments fell well within the uncertainty bounds. The estimation of spawning stock biomass followed the same trends as the official assessment, but not the same levels. We conclude that the data-limited assessment method can be used for stock assessment and that the uncertainty estimates are reliable. Further work is needed to quantify the spawning biomass of the stock. [ABSTRACT FROM AUTHOR]

The influence of riverine outputs from the Tuy River on the coastal processes of near sandy beaches was assessed by measuring the physical and chemical characteristics of water and sediment samples at eight sites along the north central Venezuelan coast and from the rivers that flow through this región into the sea (Tuy, Capaya, Curiepe) during two field surveys. In addition, the behavior of the Tuy River discharge plume was evaluated using remote sensors, and its effect on the population abundance and size structure of the clam Tivela mactroides was determined. Of the three rivers evaluated, the Tuy River had the highest impact on the coastal zone (789.15 ± 190.63 km²) in terms of flow rate (246.39 m³ s-1), nutrients (659.61 ± 503.27 g s-1total nitrogen; 52 ± 53.09 g s-1 total phosphorus) and sedimentary material (9320.84 ± 9728.15 g s-1). The variables measured (salinity, total nitrogen and phosphorus, pH, turbidity, and total organic carbon) showed a spatial gradient along the coast. Tivela mactroides had the highest biomass and density (9126.8 ± 1562 g m-2; 9222.22 ± 1976.72 ind m-2 ) at the sites farthest from the river mouths and smaller sizes (< 13 mm long) at sites close to the river mouths. The Tuy River plume modifies the functioning of the coastal system processes by discharging large amounts of nutrients and sedimentary material into the water column, which are then distributed by marine currents and alongshore transport. These contributions are used by T. mactroides populations, which show high abundances and differentiation in size structure along this coastline.Para evaluar los aportes del río Tuy sobre los procesos costeros en playas arenosas cercanas, se examinó en dos campañas de muestreo, las características físicas y químicas a nivel de agua y sedimento en ocho estaciones ubicadas a lo largo de la costa centro norte de Venezuela, el cauce de los ríos que allí desembocan (Tuy, Capaya, Curiepe), además del comportamiento de la pluma del río Tuy mediante sensores remotos y su influencia sobre las poblaciones de la almeja Tivela mactroides en cuanto a abundancia y estructura de talla. El río Tuy tuvo mayor predominio sobre la zona costera (789,15 ± 190,63 km ), presentó el mayor aporte líquido (246,39 m³ s-1), de nutrientes (659,61 ± 503,27 g s-1 nitrógeno total; 52 ± 53,09 g s-1fósforo total) y material sedimentario (9320,84 ± 9728,15 g s-2 ). Existe un gradiente espacial de las variables medidas a lo largo de la costa (salinidad, nitrógeno y fósforo total, pH, turbidez, carbono orgánico total). Tivela mactroides presentó mayor biomasa y densidad (9126,8 ± 1562 g m-2 ; 9222,22 ± 1976,72 ind m-2 ) en las estaciones alejadas de la desembocadura de los ríos, y presentó menores tallas (< 13 mm) en estaciones cercanas a la desembocadura de los ríos. Se concluye que la pluma del río Tuy modula el funcionamiento del sistema costero, mediante el aporte de nutrientes y material sedimentario en el agua, distribuyéndose mediante las corrientes marinas y el transporte litoral. Esto es aprovechado por las poblaciones de Tivela mactroides, presentando altas abundancias y diferenciación en la estructura de tallas a lo largo de la costa.

Neilonella sulculatais a dominant bivalve on muddy bottoms of the continental shelf and gulfs off Argentina (Southwest Atlantic). Two benthic surveys performed in 2007 and 2009 in San Jorge Gulf, a depositional area characterized by silt/clay sediments, gave us the opportunity to test whether the population of this clam displays a significant spatial structure and to analyse if there is an inverse relationship between size and density. Density, biomass and size–frequency distribution displayed significant spatial structure, being positively autocorrelated at the smallest spatial scales (c.1.7–14/17 km). Biomass also showed spatial contagion at scales of 25–33 km. A substantial increase in density and biomass occurred between 2007 and 2009. Empty valves in the sediment showed that the maximum size attained by the species may exhibit considerable variation at relatively short temporal scales. Regardless of temporal changes in density and biomass, the spatial structure of these variables remained stable. In densely populated areas, shell size decreased with increasing density, suggesting a density-dependent control of growth. A clear north–south increase in density and biomass was detected, which might be related to a gradient in food availability caused by a thermohaline frontal system associated with wind-related upwelling. [ABSTRACT FROM AUTHOR]

The analysis of plankton size distributions in response to physical and biological forcing is relevant to the understanding of marine ecological processes. In this study, we evaluated the influence of seasonal intrusions of the South Atlantic Central Water (SACW) on zooplankton vertical distribution and normalized biomass size spectra (NBSS) on the inner shelf off subtropical Brazil. Monthly sampling was performed at a fixed station for 5 years and zooplankton samples were analyzed with a ZooScan system. SACWintrusions led to increases in nitrate, chlorophyll and zooplankton biomass in different depth strata. NBSS slopes and intercepts varied between SACW intrusion and retraction phases and stratification was a key factor explaining seasonal fluctuations in NBSS parameters. The zooplankton interannual variability was related to the changing strength of SACW intrusions during the time series, as indicated by surfacing 18 and 20°C isotherms in certain years and intrusion phases, indicative of transient upwelling. We conclude that the temporal components of zooplankton variability in this subtropical coastal ecosystem were governed by SACW intrusions, affecting the vertical distribution of zooplankton biomass and size structure. [ABSTRACT FROM AUTHOR]

Zooplankton was studied seasonally between 2009 and 2011 in İskenderun Bay in order to determine temporal variations in abundance, biomass, and size structure and their relationships with environmental factors. Zooplankton sampling was performed vertically using a WP-2 net (200-µm). A total of 30 zooplankton taxonomic groups were identified. Cladocera was the dominant group, and together with Copepoda and Appendicularia constituted approximately 90% of zooplankton. In respect to abundance and biomass values, 2 peaks were observed in 2009, the first in spring and the second in autumn. However, a second peak was observed in summer in both 2010 and 2011, due to increases in cladoceran abundance. During all seasons and years of the study period, smallsized organisms (200-500 µm) constituted the majority of the zooplankton. Zooplankton abundance was influenced by environmental factors. The relationship between the abundance of zooplankton groups and environmental parameters varied according to the groups. In conclusion, clear seasonal variation and slight differences among years were observed in terms of the examined properties of the zooplankton groups. Abiotic environmental variables and availability of food were considered to particularly affect this variability. [ABSTRACT FROM AUTHOR]

Size frequency distribution, catch per unit effort (CPUE) and biomass of blue swimming crab Portunus segnis were studied in the northern Persian Gulf. A total of 1689 male and 1824 female crabs were collected by swept area method on a monthly basis from May 2010 to September 2012. The populations of male and female crabs were dominated by adult crabs (carapace width >100 mm) from December to May. The juvenile crabs were dominant from June to October and the averages of CPUE did uptrend from June to October. The CPUE increased in full moon and the highest value was observed in shallow coastal areas below 10 m and significantly decreased as depth increased. The maximum CPUE was recorded at 415 and 450 engine powers and the vessel speeds of about 2.5 and 2.8 knots. The monthly biomass estimations showed an upward trend from June to October within the study period, so that the maximum biomass was 110 tonnes in October 2011. Given the CPUE trend and biomass estimation, the results of the present study suggest that October is the optimum time as open fishery season for blue swimming crab in the northern Persian Gulf and the highest CPUE is achievable in shallow coastal areas at less than 10 m depth. [ABSTRACT FROM PUBLISHER]

Microhabitat heterogeneity with a high environmental variability affects the persistence of species and their population dynamics. This study investigated the effect of urban habitat heterogeneity on the morphological and reproductive traits as well as foliar nutrient contents of Calotropis procera. Sixty-three permanent stands (5 × 5 m) were selected to represent the micro-variations in four urban habitats of C. procera in Cairo, Egypt. C. procera populations showed significant variations in the size structure, biomass and density between the studied habitats. Size class distribution was bell- or biomodal shaped in most habitats, which suggests that C. procera adopts an adult-persistence population survival strategy. It was characterized by low episodic recruitment rates and relative stability. C. procera had significant plasticity in morphological and reproductive traits with changing of soil edaphic factors in urban habitats. Foliar Na, K and P concentrations were significantly different in the studied habitats, in addition to their significant correlations with the same elements in soil. The variation in the functional traits of the plant indicated its ability to persist under urban habitat conditions. It is likely that C. procera may dominate in the future the urban habitats under extensive degradation of the natural habitats of native species. [ABSTRACT FROM AUTHOR]

Kocum, E. and Sutcu, A., 2014. Analysis of variations in phytoplankton community size-structure along a coastal trophic gradient. The phytoplankton community size structure is a significant factor in the ecological and biogeochemical functioning of marine ecosystems. Various environmental factors, including nutrients, can cause variations in the size structure of phytoplankton community, ultimately determining the potential for downward carbon transport and productivity in marine ecosystems. In the present study, microscale spatial variation in phytoplankton size structure was investigated at two coastal stations having different nutrient environments. The variation in phytoplankton size structure was characterized by a significantly ( p < 0.05) higher contribution of larger cells and diminishing abundance of picoplankton under increasing nutrient concentrations observed at both sites, although at different threshold unfractionated phytoplankton chlorophyll a biomass levels. The average percent contributions of picoplankton to total biomass were 30.02 and 19.07% at less enriched site I and at enriched site II, respectively. Thus, we concluded that the variation in phytoplankton size structure was led by the factors that regulated the contribution of large phytoplankton cells; that is, the dominance of picoplankton was only possible when nutrient concentrations precluded accumulation of the larger size classes in the phytoplankton community. Bu çalışmada Çanakkale Boğazı kıyılarında trofik bakımdan farklılık gösteren iki bölgede fitoplankton komünitesi büyüklük yapısındaki değişim incelenmiştir. Nutrient bakımından zengin bölgede ve toplam fitoplankton biyokütlesi arttığında ise her iki bölgede fitoplankton komünitesindeki büyük hücreli üyelerin bolluğunda artma ve pikoplankton bolluğunda da düşüş gözlemlenmiştir. Çalışma sonucunda fitoplankton komünitesi büyüklük yapısındaki varyasyonun büyük hücreli üyelerin artışını engelleyen koşullarca düzenlendiği yani, pikoplankton bolluğundaki artışın ancak büyük hücreli fitoplankton artışını sınırlayan nutrient yoğunluklarında meydana geldiği ileri sürülmüştür. [ABSTRACT FROM AUTHOR]

Plankton size structures were investigated based on estimated individual biovolumes at six typical stations of Daya Bay in the summer (August 2010) and winter (January 2011). The biomass size distribution (BSD) and the number size spectra (NSS) of plankton were established to analyze plankton size structures from taxonomic and ataxonomic perspectives, respectively. In Daya Bay, the phytoplankton individual biovolume was in the range of 64–496,757µm3, and the zooplankton individual biovolume was in the range of 1.15×106–5.23×1011 µm3. The average biomasses of phytoplankton and zooplankton were 1.60mgL−1 and 1.19mgL−1 in the summer, and .42mgL−1 and .35mgL−1 in the winter, respectively. The ranges of the NSS slope were −1.94 to −.75, −2.60 to −.69, and −2.11 to −1.64 for phytoplankton, zooplankton, and total plankton, respectively. The ranges of the NSS intercepts were 13.17 to 23.97, −3.19 to 38.88, and 20.14 to 27.86 for phytoplankton, zooplankton, and total plankton, respectively. Our results indicate that the thermal water discharge from nuclear power plants, aquaculture and riverine nutrients significantly influenced the BSD and NSS patterns of plankton in Daya Bay. Moreover, the influence of aquaculture was more significant in the summer, and the influence of thermal water discharge was more significant in the winter. In general, a steeper NSS slope usually suggested more human-induced perturbations. The NSS parameters well reflected the horizontal variations of the environmental characteristics between these stations. [ABSTRACT FROM AUTHOR]

Analysis of conditions of formation of microplanktonic microbial communities (MC) was carried out for the Pechora Sea using the data of winter 2002-2005. The patterns of distribution of different MC groups in different water types are discussed. Regular variations of the indices of abundance in a gradient of physicochemical variables were revealed. The estimated average bacterial numbers for under-ice conditions were 234 × 10 cells/mL, with the average cell volume of 0.58 μm and total cell area ∼550 mm/L. The estimated total microbial biomass in the 0-25 m water horizon of the Pechora Sea is 187 × 10 g wet biomass. [ABSTRACT FROM AUTHOR]

Little attention has been paid to small copepods and other zooplankton inhabiting pelagic ecosystems of the Southwestern Atlantic Ocean under the influence of the Antarctic Circumpolar Current circulation, despite their important role in the trophic chain and fisheries. This study gives a synoptic view (January 2001) of the micro and mesoplankton size fractions and normalized biomass size spectra (NBSS) in upper waters of five different ecological domains (shelf and oceanic Subantarctic and Antarctic waters) including the Brazil–Malvinas confluence (BMC). Copepods were always the main component of the zooplankton; the <300-µm fraction represented between 70 and 99% in terms of numbers and from 20 to 88% in terms of biomass. Other zooplankton contributed with <40% to total zooplankton densities, though showing some biomass peaks (>50%). Chlorophyll a, sea surface temperature and salinity were the environmental variables that best explained the distribution trend of zooplankton, mainly that of the <300-µm fraction. For all the domains, NBSS revealed flat slopes (−0.6 to −1), suggesting a higher proportion of large organisms than expected at equilibrium. A dome-shape feature was detected in the BMC. Total biomass and trophic levels of the system were related to the composition of the community and the hydrological conditions of the domains covered. [ABSTRACT FROM AUTHOR]

Spatial variability of plankton biomass, community composition and size structure was investigated across a strong frontal transition (A-Front) in the southern California Current Ecosystem in October 2008. Depth profiles were taken across a 25-km transect of nine stations sampled semi-synoptically during one night and for 3 days following drifter arrays in the adjacent water masses. Community compositions are compared based on analyses by digital epifluorescence microscopy, flow cytometry and pigment composition by high-pressure liquid chromatography. Our results show three assemblages sharply delineated in space, with plankton at the front being compositionally distinct and biomass elevated relative to either of the adjacent water masses. Depth-averaged chlorophyll a (Chl a) varied by a factor of 2.3 (0.35–0.81 µg Chl a L−1) and autotrophic carbon (AC) varied almost 3-fold (13.6–35.4 µg C L−1) across the front. One of the most striking features was a sharp gradient in the distribution of Prochlorococcus (PRO) and Synechococcus (SYN), with PRO located in the warmer oligotrophic waters on the south side of the front and SYN located in the cooler mesotrophic waters to the north. Both PRO and SYN had local biomass minima directly at the front. The peak in phytoplankton biomass at the front was dominated by large (>20 µm) diatom cells, comprising 71% of the total community biomass. In contrast to previous studies of frontal features in the southern California Current, our study of the A-Front shows strong frontal enhancement of phytoplankton biomass and a shift of phytoplankton size structure towards larger cells. [ABSTRACT FROM AUTHOR]

The distribution of summer phytoplankton across the Straits of Magellan (SOM) was studied with the aims of tracing differences among the distinct subregions of the area and contributing to the knowledge of its biodiversity. Samples collected at 25 stations were observed and counted in light microscopy. Selected samples were observed with transmission electron microscopy. The main unifying feature of the phytoplankton in the SOM was the high abundance and numerical dominance of small-sized (<10 μm) eukaryotic species, among which coccoid cells of <3 μm size were predominant (56.2 ± 30.6 of the total phytoplankton abundance). They mostly belonged to the prasinophyte Pycnococcus provasolii, which was abundant (0.8-6,834 cells × 10 ml) at all stations with the exception of those in proximity to the Atlantic entrances, where it was not recorded. Small-sized (<3 and 3-5 μm) diatoms ( Minidiscus trioculatus, Lennoxia faveolata and other undetermined centric species) attained high densities (<3,757 cells 10 ml) especially at stations of the Patagonian sectors, whereas microplanktonic diatoms were only found at the two entrances of the Straits. Dinoflagellates were constituted mainly by >10 μm forms in the Andean subregion and <10 μm naked species in the Patagonian subregion, contributing up to 75.9 and 41.8% of the total carbon in these two areas, respectively. In the Patagonian subregion, flagellates mainly constituted by <5 μm forms and by cryptomonads <10 μm comprised up to 53.9% of the total biomass. Several species identified in this study have never been reported in other investigations in the SOM, while others, including Pycnococcus provasolii and Lennoxia faveolata, have rarely been recorded elsewhere. Overall, the summer phytoplankton of the Straits does not resemble that of any other region of the world's seas. Although some of the predominant species might have been overlooked elsewhere, their abundance and relative importance apparently constitute a distinctive feature of the SOM. [ABSTRACT FROM AUTHOR]

Gnanadesikan, A., Dunne, J. P., and John, J. 2011. What ocean biogeochemical models can tell us about bottom-up control of ecosystem variability. – ICES Journal of Marine Science, 68: 1030–1044.Processes included in earth system models amplify the impact of climate variability on phytoplankton biomass and, therefore, on upper trophic levels. Models predict much larger relative interannual variability in large phytoplankton biomass than in total phytoplankton biomass, supporting the goal of better constraining size-structured primary production and biomass from remote sensing. The largest modelled variability in annually averaged large phytoplankton biomass is associated with changes in the areal extent of relatively productive regions. Near the equator, changes in the areal extent of the high-productivity zone are driven by large-scale shifts in nutrient fields, as well as by changes in currents. Along the poleward edge of the Subtropical Gyres, changes in physical mixing dominate. Finally, models indicate that high-latitude interannual variability in large phytoplankton biomass is greatest during spring. Mechanisms for producing such variability differ across biomes with internal ocean processes, such as convection complicating efforts to link ecosystem variability to climate modes defined using sea surface temperature alone. In salinity-stratified subpolar regions, changes in bloom timing driven by salinity can produce correlations between low surface temperatures and high productivity, supporting the potential importance of using coupled atmosphere–ocean reanalyses, rather than simple forced ocean reanalyses, for attributing past ecosystem shifts. [ABSTRACT FROM PUBLISHER]

The influence of riverine outputs from the Tuy River on the coastal processes of near sandy beaches was assessed by measuring the physical and chemical characteristics of water and sediment samples at eight sites along the north central Venezuelan coast and from the rivers that flow through this region into the sea (Tuy, Capaya, Curiepe) during two field surveys. In addition, the behavior of the Tuy River discharge plume was evaluated using remote sensors, and its effect on the population abundance and size structure of the clam Tivela mactroides was determined. Of the three rivers evaluated, the Tuy River had the highest impact on the coastal zone (789.15 ± 190.63 km²) in terms of flow rate (246.39 m³s-1), nutrients (659.61 ± 503.27 g s-1 total nitrogen; 52 ± 53.09 g s-1 total phosphorus) and sedimentary material (9320.84 ± 9728.15 g s-1). The variables measured (salinity, total nitrogen and phosphorus, pH, turbidity, and total organic carbon) showed a spatial gradient along the coast. Tivela mactroides had the highest biomass and density (9126.8 ± 1562 g m-2; 9222.22 ± 1976.72 ind m-2) at the sites farthest from the river mouths and smaller sizes (< 13 mm long) at sites close to the river mouths. The Tuy River plume modifies the functioning of the coastal system processes by discharging large amounts of nutrients and sedimentary material into the water column, which are then distributed by marine currents and alongshore transport. These contributions are used by T. mactroides populations, which show high abundances and differentiation in size structure along this coastline. [ABSTRACT FROM AUTHOR]

Abstract: The gathering of invertebrates during low tides is a traditional activity across the Pacific islands, but it still remains poorly documented. Recreational invertebrate harvesting was investigated in 2008 and 2009 in the coastal/islet reef flats surrounding Noumea, the main urbanized area in New Caledonia (South Pacific). Human frequentation, harvesting effort, captures and their impacts on the density and size structure of the main targeted species were simultaneously quantified. Invertebrate harvesting was restricted to a 5-months winter period (April–August), depending mainly on low tides. Frequentation (∼10,000 persons year−1 for an area of 324ha) was a relevant proxy of harvesting pressure, with higher impacts on coastal flats compared to islet flats with respect to distance from city town and accessibility. On the whole, harvesters collected 8.4±0.7tyear−1 of invertebrates (more than 60 species, mainly molluscs), with a mean of 8harvestersha−1 over the year. Three clam species accounted for 50% of the total catch biomass (shell inclusive), with decreasing occurrences along the harvesting period emphasizing a reduction of the largest individuals. Harvesting-related disturbance mostly impacted the largest size classes, which constituted a minor (i.e. 3%) part of the reproductive adults. The 7-months non-harvesting period is likely to constitute a recovery period for the target species, with harvesting impacts on the natural populations less severe than initially expected. [Copyright &y& Elsevier]

Abstract: We report on the population dynamics of Dosidicus gigas off Guaymas from the 2002–2003 to 2007–2008 fishing seasons. The study was supported by the catch-at-length data of the commercial fleets. The results showed a large variation in recruitment because during some fishing seasons the recruitment was poor. This condition in the population may also be impacted by migration, a new distribution of jumbo squid in the eastern North Pacific, or the changes in the California current. We identified a pattern in the variability of recruitment. Warmer waters caused by the El Niño conditions in the California current are coincident with low recruitment. Cooler waters identified with negative anomalies in the sea surface temperature caused by La Niña were related to high recruitment. Our time-series showed a reduction in recruits and a fall in the mean biomass. For the jumbo squid fishery off Guaymas, recruitment determines trends of biomass over time. Our results also showed that for all fishing seasons the proportional escapement was between 59% and 89%, which was higher than the target level of 40%. Consequently, the harvest of jumbo squid is less than the optimum level. [ABSTRACT FROM AUTHOR]

1. Low flows in rivers are predicted to increase in extent and severity in many areas in the future, yet the consequent impacts of river drying on terrestrial communities via (i) changes to riparian microclimatic conditions and (ii) the identity and abundance of emerging aquatic insects available to riparian predators have not been quantified. 2. We investigated the influence of low river flow on a riparian fishing spider, Dolomedes aquaticus, in five New Zealand rivers containing permanently flowing and drying reaches and, in one river, along a longitudinal drying gradient. 3. The biomass of aquatic insects, potential prey for D. aquaticus, declined with low river flows while the abundance of potential terrestrial prey remained similar at all sites. In the replicate rivers, and along the longitudinal drying gradient, spider biomass was lower, and size classes were skewed towards more small and fewer large spiders, in drying sites. A desiccation experiment in the laboratory indicated high sensitivity of the spiders, with prey presence increasing spider survival. 4. Differences in the spatial distribution, biomass and population size structure of spiders were observed along the longitudinal drying gradient and disappeared within 16 days of the water returning to all sites. 5. In total, low river flow affected the biomass of D. aquaticus, as well as their size class structure and spatial distribution. This indicates that low river flows have the potential to affect adjacent terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Ecotoxicological field studies have shown that total abundance and biomass often recover shortly after pulsed toxicant stress. In contrast, population structure showed comparatively long-term alterations before reaching pre-treatment conditions. We investigated two mechanisms that may explain the prolonged recovery of population structure: latent toxicant effects on life-history traits on the individual level and competition on the population level. To test these hypotheses we exposed populations of Daphnia magna to a pulse of the pyrethroid Fenvalerate. For several generations the populations were kept at two different degrees of competition: strong competition at carrying capacity and reduced competition maintained by simulated predation. After disturbance due to Fenvalerate exposure, biomass recovered after 14–17 days. In contrast, size structure characterised by a lack of large and dominance of small organisms recovered after 43 days in populations with strong competition. Size structure recovered twice faster in populations with reduced competition. We explain this as follows: due to toxicant induced mortality, food availability and consequently birth rate increased and populations were dominated by small individuals. In populations without predation, these cohorts grew and eventually exerted high intraspecific competition that (i) stopped further growth of juveniles and (ii) increased mortality of adults. These demographic processes were mainly responsible for the prolonged recovery of size structure. In contrast, for populations with predation, the regular harvest of individuals reduced competition. Juveniles developed continuously, allowing a fast recovery of size structure in these dynamic populations. In risk assessment the duration for populations to recover from (toxicant) stress, is crucial for the determination of ecological acceptable effects. We conclude that competition needs to be considered in order to understand and predict recovery of size structure. [Copyright &y& Elsevier]

Size-selective mortality inevitably leads to a decrease in population density and exerts a direct negative effect on targeted size classes. But density and population size structure are also shaped by food-dependent processes, such as individual growth, maturation, and reproduction. Mortality relaxes competition and thereby alters the dynamic interplay among these processes. As shown by the recently developed size-structured theory, `which can account for food-dependent individual performance, this altered interplay can lead to overcompensatory responses in size class-specific biomass, with increasing mortality. We experimentally tested this theory by subjecting laboratory fish populations to a range of size-selective mortality rates. Overall, the results were in agreement with theoretical predictions. Biomass of the juvenile size class increased above control levels at intermediate adult mortality rates and thereafter declined at high mortality rates. Juvenile biomass also increased when juveniles themselves were subjected to intermediate mortality rates. Biomass in other size classes decreased with mortality. Such biomass overcompensation can have wide-ranging implications for communities and food webs, including a high sensitivity of top predators to irreversible catastrophic collapses, the establishment of alternative stable community states, and the promotion of coexistence and biodiversity. [ABSTRACT FROM AUTHOR]

The spatial distribution, biomass and size structure of key mesozooplankton species and micronekton in the Bransfield Strait (Antarctica) are described in relation to environmental variables during the austral summer 2001. Stratified (BIONESS) biological sampling at five depth-ranges and CTD casts were performed at 40 stations, including a cross-Strait transect. Six families, 11 genera and 16 species composed the total catch of larval and juvenile fish, which were more abundant in the upper 75 m. Trematomus scotti was the most abundant fish and large individuals dominated at depths >75 m. The fish distribution patterns were associated with the main water masses in the area and with bottom depth. Spatial segregation in density and biomass of krill ( Euphausia superba) and salps ( Salpa thompsoni) was observed at a relatively small scale, in relation to the main water masses. Also, size-related spatial segregation was found in krill. The present study suggests that the spatial distribution of krill, salps and early life stages of fish, are influenced by the main water masses in the Strait, and that species may adapt their reproductive strategies not only to seasonal production peaks, but to transport processes within water bodies that maximise their fitness through optimum temperature and/or trophic environments. [ABSTRACT FROM AUTHOR]

All the available data on the distribution of Zostera marina meadows in the coastal waters of Estonia, NE Baltic Sea, were analysed in order to achieve a generic idea of the historical and present status of eelgrass. Altogether 44 localities with eelgrass present were recorded in 1995. 2005 as compared to 36 sites recorded in 1959.1984. The percentage of findings in different water basins ranged from 1.3 to 5.1 in 1959.1984 compared to 0.6.3.6 in 1995.2005. This suggests that no significant decline or improvement of the eelgrass meadows has occurred in the Estonian coastal sea. Yet there are signs of a negative impact of eutrophication on eelgrass. [ABSTRACT FROM AUTHOR]

We studied the population dynamics of Sargassum lapazeanum from the southwestern Gulf of California, Mexico, between February 2000 and February 2001. We quantified the seasonal changes in frond density, stand biomass, frond size structure and inequality, presence of reproductive structures, and rates of recruitment, growth, and mortality. Fronds were present during the entire year, although with a marked seasonality: mean frond density, frond length, and stand biomass were highest in spring and lowest in winter. The strong increase in frond density between winter and spring resulted from the combination of high recruitment and low mortality rates. Growth rates were highest in spring; the highest absolute value (3.6 cm d-1) is among the highest found for brown seaweeds. The frond size structure became best developed in late spring. Reproductive structures peaked in abundance in late spring and became mostly lost by late summer. Senescence started in late spring and increased dramatically during the summer. The strong decrease in frond density between summer and autumn resulted from the combination of low recruitment and high mortality rates. In early autumn, primarily only small fronds remained in the population, including new recruits and remnants of previously large fronds. The seasonal pattern in the temporal abundance changes for S. lapazeanum agrees with a general model proposed for subtropical species of this genus. [ABSTRACT FROM AUTHOR]

Abstract: Size structure, taxonomic composition and bioturbation potential of benthic metazoan communities were examined at three contrasting sites on the northwest European continental margin as part of a wider study of biogeochemical cycling in the deep-sea benthic boundary layer. Sampling was conducted in the Hatton–Rockall Basin (1100 m depth), on the North Feni Ridge (1920 m) and in the South Rockall Trough (3580 m) on two cruises bracketing the expected 1998 spring phytodetrital flux. Density and biomass of epibenthic megafauna declined with depth and were consistent with previous data from the deep northeast Atlantic. Aggregations of the hexactinellid sponge Pheronema carpenteri occurred at 1100 m. The percentage contribution of suspension-feeders to megafaunal biomass at the lower slope sites was much higher than expected for these depths. Macrofauna (sensu stricto) were consistently undersampled by a box corer relative to an hydraulically damped multiple corer. Estimated macrofaunal densities declined with depth. Polychaete trophic group structure was very different at the three sites, with more small carnivores at 1100 m, surface deposit and interface-feeders at 1920 m, and a higher representation of subsurface deposit-feeders at 3580 m. Meiofaunal densities were low in comparison with published data from comparable depths in the northeast Atlantic. Meiofaunal numbers increased at all three sites from May to July 1998. The increase at 1920 m was statistically significant and was associated with the greatest phytodetrital accumulation observed during the study period. The relative contribution of the mega-, macro- and meiofauna to benthic metazoan biomass did not vary consistently with depth, and no trend was apparent in a review of data from other studies in the North Atlantic. Depth-related patterns in community size structure recorded from previous North Atlantic studies were not all replicated, suggesting the importance of local hydrodynamics and other environmental factors. There was no obvious link between faunal parameters and biodiffusion coefficients or mixing modes estimated from radiotracer profiles. Diffusion-analogue 210Pbexcess profiles recorded at 3580 and 1100 m resulted from a combination of macrofaunal and megafaunal sediment mixing, some of it advective. At 1920 m, a combination of deep megafaunal subduction and near-surface concentration of macrofaunal feeding activity produced subsurface radiotracer peaks. The poorly known burrowing megafauna probably play a significant role in bioturbation at all three sites. [Copyright &y& Elsevier]

Data from vertical net hauls and from a submersible optical plankton counter (OPC) were compared in terms of biomass and slope of the normalized biomass–size spectra (NB–SS), a proxy for the size structure of the community. The relationship between the estimates of biomass in the overlapping range sampled by both methods (0.2–2 mm equivalent spherical diameter (ESD)) was linear and not significantly different to 1 (BOPC:BNET=1.1±0.1, r2=0.84). However, the relationship varied depending on the size fraction considered; the ratio BOPC:BNET was 0.10±0.04 (r2=0.30), 0.8±0.2 (r2=0.66), and 2.4±0.5 (r2=0.64) for the size fractions 0.2–0.5, 0.5–1, and 1–2 mm ESD, respectively. The discrepancies between methods were presumably due to the combined effect of the limitations of the instrument in the lower detection limit and the errors in the volume of water sampled by the net for the smallest size fraction, and to net avoidance enhanced by clogging for the largest size fraction. The agreement between methods improved when the NB–SS of the different data sets were compared. The slope (b=-1.1) and the intercept (a=14.6) of the NB–SS integrated across stations were not significantly different (Student''s t-test) for the linear model fitted to net samples, OPC data, or pooled data from both methods. Station by station, the slopes of the NB–SS from the net (bNET) and the OPC (bOPC) were not significantly different in 61% of the stations. This percentage increased to 78% when the comparison was limited to the mesoplankton size range. As an example of the applicability of the OPC, we showed the distribution of mesoplankton biomass and size structure along the NW and N Iberian Shelf during the winter–spring transition of 2002 and its relationship with the hydrographic scenario. [Copyright &y& Elsevier]

This study assessed the abundance, biomass and size structure of the ctenophore Mnemiopsis sp. in the north-western (NW) Black Sea during the summer of 1995 and the spring of 1997, i.e. several years after this species became the dominant zooplankter in this area. Biomass was measured directly as wet weight and then converted to carbon units. The total population biomass was low in spring (114 mg C m−2) and peaked in July (630 mg C m−2). Spawning increased enormously when the water temperature exceeded 22 °C and was primarily restricted to coastal stations. Larval biomass was highest in the plume of the river Danube. The body length (L, in cm) and volume (V, in ml) of a large number of animals were measured in each season and related to each other according to V=a Lb. The parameters of the equation changed significantly from spring (V=0·244 L2·25) to summer (V=0·575 L1·88). With all data pooled, the equation was V=0·303 L2·268), which is similar to earlier results from other areas. Length to volume relations have been used by previous authors to calculate Mnemiopsis biomass in the Black Sea. The use of various allometric equations published in the literature resulted in estimates of the population biomass ofMnemiopsis differing by a factor of two. For a given size class, the biomass of Mnemiopsis individuals increased from spring through to late summer. The population biomass of Mnemiopsis was similar to estimates obtained from the same area in the early 1990s when comparable methods were used. Current estimates of the total biomass of Mnemiopsis are, however, subject to serious biases originating from the use of different sampling devices and methods of calculation. [Copyright &y& Elsevier]

Sargassum muticum (Yendo) Fensholt is an introduced brown seaweed with a very distinctive seasonal growth cycle on European shores. The present study links the dynamics of a population of S. muticum with the seasonal growth cycle of the species and the density-dependent processes operating throughout this cycle. Results indicate that both growth cycle and intraspecific competition influenced the structure and population dynamics. Size inequality increased during the slow growth phase (autumn–winter) of the 2-year study. Mechanisms generating inequality of size could be the existence of asymmetric competition and the inherent differences in growth rates between old (regenerated) and new thalli (recruits). Inequality of size distributions decreased progressively during the last months of the growth phase (spring–summer) and could be related to a process of self-thinning. There was a negative biomass–density relationship (as a measure of biomass accumulation-driven mortality) that confirms the importance of self-thinning as a major demographic factor in the S. muticum population. [ABSTRACT FROM AUTHOR]

Summary 1. Water beetle assemblages were sampled in each of 18 freshwater ponds, including 11 recently constructed sites designed to provide mitigation for wetlands destruction elsewhere, and seven older reference sites. There were three objectives: (a) to relate taxon richness and biomass of the beetles to the same properties of the wider aquatic invertebrate community, (b) to evaluate changes in beetle assemblage structure over time, and (c) to determine habitat effects on taxonomic composition, mean body size and trophic guild structure of the beetle assemblage. 2. Forty-seven beetle genera were identified, representing 77 species. The beetles represented an average of 21.5% of total generic richness, but only 3.7% of total wet biomass of the wider invertebrate community. 3. Of all variables evaluated using canonical correspondence analysis (CCA), site age had the greatest influence on the beetle assemblage. Predatory dytiscids were early colonists at younger sites, while herbivorous curculionids and chrysomelids associated with particular types of vegetation typically occurred in older ponds. Mitigation ponds and reference ponds supported similar numbers of species. Reference sites, however, harboured substantially more unique species found at only a single site within the study area. 4. The presence of fish was also strongly related to beetle assemblage structure. Ponds with few or no fish contained about 3-fold higher biomass and 3-fold greater mean wet weight per individual compared to ponds with substantial fish assemblages. 5. Beetle assemblage composition varied among sites and sampling years, but beetle biomass, richness and species composition may be useful tools in evaluating the success of wetland mitigation efforts. [ABSTRACT FROM AUTHOR]

The distribution, abundance, biomass, and community structure of macrozooplankton were investigated in relation to oceanographic conditions in the Barents Sea during summer 2013, using an IKS-80 net (0.5 m2 mouth opening, 550 μm mesh). Overall, we found 20 taxa (11 in Murmansk Coastal Water-MCW and in Atlantic Water-AW, 13 in Arctic Water-ArW, and 19 in Barents Sea Water-BSW). Total macrozooplankton abundance varied between 36 and 1116 ind. m−2 (0.2–4.6 ind. m−3) with a mean value of 238 ± 34 ind. m−2 (1.0 ± 0.1 ind. m−3) for the entire area. Although the catch was fairly diverse, a small number of species accounted for the majority of the total abundance and biomass. The most abundant taxa were Parasagitta elegans (MCW, AW, BSW, ArW), Thysanoessa spp. larvae (MCW, AW), Mertensia ovum (BSW), Aeginopsis laurentii (BSW), Dimophyes arctica (ArW), and Themisto libellula (ArW). Total macrozooplankton biomass ranged from 17 mg dry mass (DM) m−2 (0.1 mgDM m−3) to 6710 mgDM m−2 (23.1 mgDM m−3), averaging 1058 ± 240 mgDM m−2 (4.3 ± 0.9 mgDM m−3) across the study area, with Parasagitta elegans dominant by biomass. Cluster analysis revealed three communities (southern, central and northern) which demonstrated clear variations with latitude. Canonical correspondence analysis showed that location (latitude) and environmental conditions (mean temperature, salinity, mean phytoplankton abundance and biomass) explained 36% of the spatial variability in macrozooplankton communities. In BSW, there was a strong positive correlation between total macrozooplankton biomass and mesozooplankton stock suggesting an important role for food availability in controlling macrozooplankton variability. Predator–prey interactions also might play an important role in influencing the spatial distribution of macrozooplankton. The results may be useful as basis for future investigations of macrozooplankton in order to detect possible influence of changing environment on plankton communities of the Barents Sea during modern warming trend in the Arctic. • The diversity and evenness of the macrozooplankton increased from the south to the north. • Maximum macrozooplankton biomass was associated with frontal zones. • Environmental variables including water temperature and latitude determined macrozooplankton variability. • A clear correspondence between macrozooplankton three water regions was found. [ABSTRACT FROM AUTHOR]