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Offshore wind farms often co-occur with biodiverse marine ecosystems with high ecological, economic, and cultural value. Yet there are many uncertainties about how wind farms affect marine organisms and their environment. The before–after–control–impact (BACI) design, an approach that compares an impact location with an unaffected control both before and after the intervention, is the most common method used to study how offshore wind farms affect finfish. Unfortunately, this design has several methodological limitations that undermine its ability to detect effects in these studies. An alternative approach, the before–after-gradient (BAG) design, would sample along a gradient with increasing distance from the turbines both before and after the intervention, and could overcome many of the limitations of BACI. The BAG design would eliminate the difficult task of finding a suitable control, allow for the assessment of the spatial scale and extent of wind farm effects, and improve statistical power by incorporating distance as an independent variable in analytical models rather than relegating it to the error term. This article explores the strengths and weaknesses of the BACI and BAG designs in the context of offshore wind development and suggests an approach to incorporating the BAG design into existing fisheries surveys and a regional monitoring framework. [ABSTRACT FROM AUTHOR]

Offshore wind farms are becoming increasingly common in the coastal margins of marine ecosystems worldwide. Yet, the effects that wind farm structures have on fish populations remain unclear. To explore potential effects, a meta-analysis of studies that have examined the abundance of finfish inside of wind farms compared to nearby reference sites was conducted. Using well-established meta-analytic methods, the overall effect size across all studies was calculated, and then changes in effect size for soft-bottom and complex-bottom oriented species were explored in association with several covariates including characteristics of the wind farm (depth, distance from shore, wind farm age), the sampling design (season, gear type, and distance from the turbine sampled), and ecosystem level characteristics (functional feeding group and fishing presence/absence). The overall effect size was positive and significantly different from zero, indicating greater abundance of fish inside of wind farms. Likewise, positive and significant effect sizes were noted for several covariates for both soft-bottom and complex-bottom species. The findings of this study underscore the need for regional, national, and international collaboration on monitoring approaches and data sharing in order to develop a more holistic understanding of how offshore wind farms affect living marine resources. [ABSTRACT FROM AUTHOR]

A multistep invasive species methodology was used to evaluate the probability that the deployment of sterile non-native oysters (Crassostrea ariakensis,called Asian oyster) in field-based aquaculture could give rise to a reproductive population in Chesapeake Bay. Several pathways that could potentially lead to the unintentional release of reproductiveC. ariakensisfrom aquaculture were identified. For the four quantifiable pathways, a probability was estimated for each step based on knowledge of ecological rates. A conservative estimate for the number of reproductiveC. ariakensisthat could arise over one spawning season at a hypothetical aquaculture site was estimated. A statistical expansion of this probability estimated that it is highly likely that the cultivation of putatively sterileC. ariakensiswould initiate a reproductive population in Chesapeake Bay over a 10-year time span. The potential benefits of restoration actions involving non-native species in estuarine ecosystems must be weighed against potential ecological risks. A probabilistic approach can provide a useful method for summarizing the risk of an unintended introduction that may occur despite a reasonable and presumably “safe” approach for realizing benefits of a non-native species in aquaculture. The results presented here have important implications for future proposals involving the commercial use of non-native species in natural ecosystems. [ABSTRACT FROM AUTHOR]

Methratta, E.T., and Link, J.S. 2012. Feeding hotspots for four northwest Atlantic groundfish species. — ICES Journal of Marine Science, 69: 1710–1721.We used predator distribution and stomach content data to estimate the annual per capita rate of consumption for four representative predator species from the northwestern Atlantic Ocean, and considered how consumption is influenced by depth, bottom salinity, sediment grain size, location variables, and species-specific diet components. We found that geographic variables and species-specific prey resources were significantly associated with consumption rates, a pattern consistent with predator-prey theory. Prey categories comprised of fish were particularly important for a more mobile predator (silver hake Merluccius bilinearis), whereas benthic invertebrate prey were consistently important for a more sedentary predator (little skate Raja erinacea). Hotspots in consumption rates that overlap with particular prey resources were highlighted by the significance of location variables (longitude) for winter flounder Pseudopleuronectes americanus, silver hake, little skate, and sea raven Hemitripterus americanus. Depth was an important explanatory factor for consumption by little skate, but the explanatory value of abiotic habitat factors was low for the other three species. Greater emphasis on species-specific food habits, migratory patterns, and ecological interactions at the synoptic scales relevant to fisheries is needed for fisheries management. [ABSTRACT FROM PUBLISHER]

Small changes in environmental conditions can unexpectedly tip an ecosystem from one community type to another, and these often irreversible shifts have been observed in semi-arid grasslands, freshwater lakes and ponds, coral reefs, and kelp forests. A commonly accepted explanation is that these ecosystems contain multiple stable points, but experimental tests confirming multiple stable states have proven elusive. Here we present a novel approach and show that mussel beds and rockweed stands are multiple stable states on intertidal shores in the Gulf of Maine, USA. Using broad-scale observational data and long-term data from experimental clearings, we show that the removal of rockweed by winter ice scour can tip persistent rockweed stands to mussel beds. The observational data were analyzed with Anderson’s discriminant analysis of principal coordinates, which provided an objective function to separate mussel beds from rockweed stands. The function was then applied to 55 experimental plots, which had been established in rockweed stands in 1996. Based on 2005 data, all uncleared controls and all but one of the small clearings were classified as rockweed stands; 37% of the large clearings were classified as mussel beds. Our results address the establishment of mussels versus rockweeds and complement rather than refute the current paradigm that mussel beds and rockweed stands, once established, are maintained by site-specific differences in strong consumer control. [ABSTRACT FROM AUTHOR]

The interplay between local and large spatial scale processes in open systems is often dependent upon ecological context and species specific factors such as longevity, dispersal capability, or vulnerability to predation. When disturbance clears patches in open systems, the successful reestablishment of adult colonizers and the trajectory of succession may depend upon both the scale of the disturbance event and scale of life history characteristics. Here we examine the links between the size of a disturbance event and long. term patterns of variation in recruitment, density, and percent cover in a relatively short-lived but long-range disperser, the acorn barnacle Semibalanus balanoides, and a relatively long lived and short range disperser, the fucoid alga Fucus vesiculosus. Further, a model of linked scale-dependent processes is developed and we explore how long term patterns of scale- dependent recruitment are related to successful establishment of adults. Recruitment, densities, and cover were monitored for five years for both species in a single experiment using clearings of different sizes spread over two north-facing and two south-facing bays on Swan's Island, Maine, USA. Barnacle recruitment was particularly variable in small clearings and was lower overall at more interior sites within bays. While local-scale factors also strongly influenced patterns of variation in fucoid recruitment, fucoids dominate surface cover in large clearings and in south-facing bays. Recruitment was a poor predictor of density, whereas density itself was a good predictor of percent cover for both species. These results indicate that scale dependencies, location-specific factors, and life history traits contribute to patterns of community development on rocky shores and may ultimately determine whether an open patch converges to or diverges from its initial community state. [ABSTRACT FROM AUTHOR]

Abstract: Predictions based on theory of multiple stable states suggest that larger perturbations should lead to more unpredictable patterns of succession. This prediction was tested in the Gulf of Maine using data from 60 intertidal plots of varying size that were experimentally cleared of the rockweed Ascophyllum nodosum and from 14 benchmark sites from throughout the Gulf. Rockweed was removed from the experimental clearings ranging from 1 to 8 m in diameter in 1996 and data collected in 2004 were used to test effects of clearing size and location on divergence and variability in species composition. Benchmark data were collected in 2005, and the 14 sites were from a dataset on 53 sites throughout the Gulf of Maine. The selected sites were randomly chosen from all sites with >80% canopy cover by A. nodosum and were expected to be similar to uncleared control plots from the experiment. Experimental removal of A. nodosum resulted in clearings at 12 sites within 4 bays. Abundances of gastropods, barnacles, mussels, and fucoid algae and the percentage cover of barnacles, mussels, fucoid algae, bare space, and other species were sampled. CAP and PERMDISP analyses revealed significant differences in multivariate dispersion and variability with both clearing size and location. Variability generally increased with clearing size and location effects were related to the north–south positioning of the sites. Benchmark sites were similar to the experimental control plots but as variable as the largest clearings. Results suggest that succession in larger clearings has been more unpredictable than in small clearings. The pattern of variability in the experimental clearings is consistent with the predictions of multiple stable states. However, the large amount of variation among the benchmark sites was due to mussels and was unexpected. This unexpected variability underscores the importance of sampling benchmark sites as part of experiments. [Copyright &y& Elsevier]

Abstract: In the development of ecosystem-based fisheries management, the assessment of ecosystem status is a key element. There are many indicators that can be used to assess the status of an ecosystem that are representative of key ecosystem processes and properties. Yet, of the several hundred indicators available to evaluate marine ecosystems, which are the best to use? We evaluated multiple biotic indicators from the Northeast U.S. large marine ecosystem (LME) to determine their potential utility in assessing ecosystem status, with a particular emphasis on the fish community and fishing pressure. For those 26 indicators which met our selection criteria, we executed a multivariate ordination to evaluate how indicators group together rank in terms of explanatory power, and are weighted relative to one another. The ordination procedure also revealed indicator redundancies. We recommend a set of eight candidate indicators for routine monitoring that are both representative of major processes and sensitive to fishing-related ecosystem changes. Finally, we briefly explore the role these indicators might have in ecosystem-based fishery management. [Copyright &y& Elsevier]

Recent studies suggest that nutrient variation influences rocky intertidal community structure, however empirical evidence is rare. In the Gulf of Maine, tidepools that occur on seagull feeding roosts are potentially subjected to regular nutrient loading from seagull guano. The results of a survey conducted on Swan''s Island, ME show that roost tidepools have very low macroinvertebrate and macroalgal diversity as well as very high phytoplankton biomass compared to non-roost tidepools. An experiment presented here tested basic food chain hypotheses in tidepool communities. These basic food chain models predict that in a tidepool with one trophic level (phytoplankton only), phytoplankton biomass will increase when nutrients are enriched. In contrast, these models predict that in two trophic level tidepools (phytoplankton and mussels) herbivory will prevent an increase in phytoplankton biomass when nutrients are enriched. A short term 2×2 factorially designed field experiment was used to test this basic conceptual model using herbivory by mussels and enrichment with nitrogen as the main effects. The results of this investigation are consistent with the predictions of basic food chain models, and indicate that over the short time interval of a few days, herbivory by mussels is sufficient to maintain low phytoplankton levels following enrichment with nitrogen. Experimental enrichment with phosphorus in this study had no effect on phytoplankton biomass. The results of this study suggest that periodic pulses of nitrogen into tidepools will have little effect on phytoplankton biomass when mussels are present and that longer-term chronic nitrogen influxes may be driving the patterns of community structure in tidepools occurring on roosts. [Copyright &y& Elsevier]