Search

The clown anemonefish ‘Nemo’ Amphiprion ocellaris is the most popular fish species in the global marine ornamental trade and also its host sea anemones Heteractis magnifica, Stichodactyla gigantea, and Stichodactyla mertensii are traded. However, total catch and the potential impact of exploitation of these target organisms in Spermonde Archipelago, Indonesia, are not known. Therefore, the main objective of this study was to investigate the impact of the fishery on populations of A. ocellaris and its host anemones and how management could be improved. In order to obtain a comprehensive view on the marine ornamental fishery and trade of these species in Spermonde, this study also investigated the socioeconomics of the marine ornamental fishery and the catch records for A. ocellaris and it's host anemones. The study revealed that both, A. ocellaris and sea anemone densities were significantly lower at coral reefs with high exploitation (HE) than at reefs with low exploitation (LE). The total body length and group size of A. ocellaris was also significantly smaller at HE than at HL sites. The yearly amount traded by middlemen is estimated to 140 000 specimens of A. ocellaris and 31 000 anemones. The socioeconomic analysis showed that educational level of marine fishermen family members was low; most of them only finished elementary school. The household income analysis showed that marine ornamental fishery was not the major source of income, covering 13−43% of the expenses, with the exception of one studied island (84%). These findings revealed a considerable negative impact of marine ornamental fishery on the target populations and therefore, the implications for management strategies and conservation are discussed, including fish size restrictions for collectors, marine protected areas and regular monitoring of the amount of trade at middlemen.

It is unclear whether habitat degradation correlates with tolerance of marine invertebrates to abiotic stress. We therefore tested whether resistance to climate change-related stressors differs between populations of the green mussel Perna viridis from a heavily impacted and a mostly pristine site in West Java, Indonesia. In laboratory experiments, we compared their oxygen consumption and mortality under lowered salinity (-13 and -18 units, both responses), hypoxia (0.5 mg/l, mortality only) and thermal stress (+7 degrees C, mortality only). Mussels from the eutrophied and polluted Jakarta Bay showed a significantly smaller deviation from their normal oxygen consumption and higher survival rates when stressed than their conspecifics from the unaffected Lada Bay. This shows that human induced habitat degradation correlates with mussel tolerance to environmental stress. We discuss possible mechanisms - e.g. the selection of tolerant genotypes or habitat-specific differences in the nutritional status of the mussels - that could explain our observation.

The Laptev Sea is a high-Arctic epicontinental sea north of Siberia (Russia) that is one of the least understood regions of the world’s ocean. It is characterized by a shallow and broad shelf plateau, high influx of river water, sediments and nutrients during summer, long-lasting sea-ice cover from October to May, and the formation of a narrow flaw-lead polynya off the fast-ice edge during winter. Here, we describe results of a German–Russian research project (1993-present), presenting the distribution patterns and dynamics of its marine flora and fauna, as well as pathways and processes of coupling between sea-ice, water-column and sea-floor biota. Three ecological zones are distinguished along a combined east–west and Lena-impact gradient, differing in the composition of pelagic and benthic communities. In general, high Chl a concentrations in the sediments indicate a tight coupling between sympagic and pelagic primary production and nutrient supply to the benthos throughout the entire Laptev Sea. However, there were pronounced regional differences between the ecological zones in magnitude of primary production and trophic dynamics. Primary production during the ice-free summer was highest in the estuarine zone most strongly influenced by the Lena River (210 mg C m −2 day −1 ). The western and northeastern Laptev Sea yielded 55 and 95 mg C m −2 day −1 , respectively. Moreover, the zones differed in the partitioning of carbon flux between zooplankton and benthic food webs. In the Lena zone zooplankton carbon demand was about 31 mg C m −2 day −1 whereas in the western zone it was 21 mg C m −2 day −1 and in the eastern zone 4 mg C m −2 day −1 . Total benthic carbon demand was 32 mg C m −2 day −1 for the Lena zone, 56 mg C m −2 day −1 in the western zone and 100 mg C m −2 day −1 in the northeastern zone. A carbon budget constructed for the Laptev Sea indicates that (1) a high proportion of primary production is channelled through the benthic trophic web, bypassing the pelagic trophic web, and (2) autochthonous primary production in the northeastern and western Laptev Sea might not be sufficient to fuel both pelagic and benthic secondary production and, hence, input of allochthonous organic carbon is required to balance the overall carbon demand.

Sediments sampled during summers 1999–2002 with the German ice-breaker RV “ Polarstern ” were analyzed to estimate benthic microbial activity and biomass of the smallest sediment-inhabiting organisms (size range: bacteria to meiofauna) along a channel system in the deep western Greenland Sea at about 75°N. Biochemical investigations were expanded by direct counts of bacteria and meiofaunal organisms, including foraminiferans. A total of 36 stations was sampled along the Ardencaple Canyon, extending over 200 km in north-easterly direction from the Greenland continental rise towards the central Greenland Basin. Stations were grouped in defined regions, generally with sampling sites inside the canyon plus accompanying sites on the northern and southern levees. An additional eight stations were sampled along a depth transect crossing the Greenland continental margin and traversing the channel in its midsection. All parameters investigated confirmed no differences between stations within the channel compared to stations on the levees, opposing the hypothesis that the Ardencaple Canyon displays a major pathway for suspension-driven shelf drainage flows. However, investigations showed some general trends in the data: parameters indicating food availability at the seafloor and total microbial biomass generally decreased with increasing water depth and distance from the Eastern Greenland continental margin. Along the depth transect crossing the Greenland margin both parameters exhibited increased values at deep stations on the continental rise. The position of these stations coincides with the position of the ice edge during sampling in summer 2000. Increased food availability and microbial biomass in the sediments most probably reflect raised levels of primary productivity and enhanced sedimentation in the marginal ice zone, thereby pointing to a close pelago-benthic coupling. Bacterial activities in the sediments showed a different picture with generally increasing values with increasing distance from the continental margin, which could probably be explained by a change in bacterial assemblages.

Although the use of deep-sea imagery considerably increased during the last decades, reports on nekton falls to the deep seafloor are very scarce. Whereas there are a few reports describing the finding of whale carcasses in the deep north-eastern and south-eastern Pacific, descriptions of invertebrate or vertebrate food-falls at centimetre to metre scale are extremely rare. After 4 years of extensive work at a deep-sea long-term station in northern polar regions (AWI-“Hausgarten”), including large-scale visual observations with various camera systems covering some 10 000 m 2 of seafloor at water depths between 1250 and 5600 m, this paper describes the first observation of a fish carcass at about 1280 m water depth, west off Svalbard. The fish skeleton had a total length of 36 cm and an approximated biomass of 0.5 kg wet weight. On the basis of in situ experiments, we estimated a very short residence time of this particular carcass of about 7 h at the bottom. The fast response of the motile deep-sea scavenger community to such events and the rapid utilisation of this kind of organic carbon supply might partly explain the extreme rarity of such an observation.