Search

Climate change impacts are pronounced at high latitudes, where warming, reduced sea-ice-cover, and ocean acidification affect marine ecosystems. We review climate change impacts on two major gateways into the Arctic: the Bering and Chukchi seas in the Pacific and the Barents Sea and Fram Strait in the Atlantic. We present scenarios of how changes in the physical environment and prey resources may affect commercial fish populations and fisheries in these high-latitude systems to help managers and stakeholders think about possible futures. Predicted impacts include shifts in the spatial distribution of boreal species, a shift from larger, lipid-rich zooplankton to smaller, less nutritious prey, with detrimental effects on fishes that depend on high-lipid prey for overwinter survival, shifts from benthic- to pelagic-dominated food webs with implications for upper trophic levels, and reduced survival of commercially important shellfish in waters that are increasingly acidic. Predicted changes are expected to result in disruptions to existing fisheries, the emergence of new fisheries, new challenges for managing transboundary stocks, and possible conflicts among resource users. Some impacts may be irreversible, more severe, or occur more frequently under anthropogenic climate change than impacts associated with natural variability, posing additional management challenges. [ABSTRACT FROM AUTHOR]

The determination of the causes for the changes in marine environment in areas with similar oceanic climate forcing on most suitable sites for scallop aquaculture can help to ensure long-term sustainability of the coastal ecosystem. This study assessed aquaculture suitability sites using dominant indicators of marine ecological dynamics on Japanese scallop culture in Funka and Mutsu Bays, Japan as comparative examples. Data sources comprised of Moderate Resolution Imaging Spectroradiometer ( MODIS), four dimensional-variational (4D- VAR) data assimilation system, Advanced Land Observing Satellite ( ALOS), in situ and buoy measurements. The suitable sites were ranked on a scale of 1 (least suitable) to 8 (most suitable). In the most suitable sites in aquaculture operational areas, Funka Bay had a high proportion (51.1%) than Mutsu Bay (13.7%) for the best performed model. Peaks of aquaculture suitability scores were attributed to potential effects of currents. Extreme sea temperatures (>24°C) in summer 2010 were associated with low performance of the 2010 model in Mutsu Bay and mortality of scallops based on sea temperature-depth visualizations. Future global warming effects are likely to decrease the most suitable culture sites in Funka Bay and loss of similar areas in Mutsu Bay. Thus, change in marine environment influences scallop culture development. Such concepts could form scientific basis for aquaculture planning on designated system of larval distribution and stock management of cultured species to minimize mortality and economic losses. [ABSTRACT FROM AUTHOR]

Since 1997, ocean color satellite images have revealed large-scale blooms of the coccolithophorid Emiliania huxleyi in the eastern Bering Sea. The blooms are often sustained over several months and have caused ecosystem changes in the Arctic Ocean, as well as in the Bering Sea. We examined continental shelf sediment profiles of alkenone, a biomarker for E. huxleyi, covering the past ∼70 years. The alkenone records suggest that large E. huxleyi blooms are a novel feature in the Bering Sea as they have occurred only since the late 1970s. Recent changes in alkenone content were closely related to the 1976-77 climatic regime shift in the North Pacific, implying that warming and freshening of Bering Sea waters promoted E. huxleyi blooms. The production rate of diatoms (total valves in sediment samples), the dominant primary producers in the Bering Sea, also increased during the past several decades. However, the ratio of alkenone content to total diatom valves in the sediments increased as E. huxleyi production increased, suggesting that the increase in the E. huxleyi production rate frequently exceeded the increase in the diatom production rate. Overall, our results indicate a possible subarctic region ecosystem shift driven by climate change. [ABSTRACT FROM AUTHOR]

Abstract: Chlorophyll-a (chl-a) concentration has an important economic effect in coastal and marine environments on fisheries resources and marine aquaculture development. Monthly climatologies the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) derived chl-a from February 1998 to August 2004 around Funka Bay were used to investigate the spatial and temporal variability of chl-a concentrations. SeaWiFS-derived suspended sediment, MODIS derived sea surface temperature (SST), solar radiation and wind data were also analyzed. Results showed two distinct chlorophyll blooms in spring and autumn. Chl-a concentrations were relatively low (<0.3mgm− 3) in the bay during summer, with high concentrations occurring along the coast, particularly near Yakumo and Shiraoi. In spring, chl-a concentrations increased, and a large (>2mgm− 3) phytoplankton bloom occurred. The spatial and temporal patterns were further confirmed by empirical orthogonal function (EOF) analysis. About 83.94% of the variability could be explained by the first three modes. The first chl-a mode (77.93% of the total variance) explained the general seasonal cycle and quantified interannual variability in the bay. The spring condition was explained by the second mode (3.89% of the total variance), while the third mode (2.12% of the total variance) was associated with autumn condition. Local forcing such as the timing of intrusion of Oyashio water, wind condition and surface heating are the mechanisms that controlled the spatial and temporal variations of chlorophyll concentrations. Moreover, the variation of chlorophyll concentration along the coast seemed to be influenced by suspended sediment caused by resuspension or river discharge. [Copyright &y& Elsevier]

Abstract: River plumes have important effects on marine ecosystems. Variation in the extent and dispersal of river plumes is often associated with river discharge, wind characteristics and ocean circulation. The objectives of this study were to identify the Tokachi River plume by satellite, determine its relationship with river discharge and clarify its temporal and spatial dynamics. SeaWiFS multispectral satellite data (normalized water-leaving radiance: nL w) with 1.1km spatial resolution were used to determine the spatial and temporal variability of the plume during 1998–2002. Supervised maximum likelihood classification using six channels of nL w at 412, 443, 490, 510, 555 and 670nm with each band''s spectral signature statistic was used to define classes of surface water and to estimate the plume area. Supervised maximum likelihood classification separated three to four classes of coastal water based on optical characteristics as a result of wind stress events. The satellite-observed plume area was correlated with the amount of river discharge from April to October. The plume distribution patterns were influenced by wind direction and magnitude, the occurrences of a near-shore eddy field and surface currents. Empirical orthogonal function (EOF) was used to express the spatial and temporal variability of the plume using anomalies of nL w(555) monthly averaged images. The first mode (44% of variance) showed the turbid plume distribution resulting from re-suspension by strong wind mixing along the coast during winter. This mode also showed the plume was distributed along-shelf direction in spring to early autumn. The second mode (17% of variance) showed spring pattern across-shelf direction. EOF analysis also explained the interannual variability of the plume signature, which might have been affected by the flow of the Oyashio Current and the occurrence of a near-shore eddy field. [Copyright &y& Elsevier]

Short- and long-term climate oscillations impact seascapes, and hence, marine ecosystem structure and dynamics. Here, we explored the spatio-temporal patterns of potential squid habitat in the western and central North Pacific across inter-decadal climate transitions, coincident with periods of persistent warming and cooling. Potential habitat distributions of Ommastrephes bartramii were derived from the outputs of multi-ensemble species distribution models, developed using the most influential environmental factors to squid distribution and occurrence data. Our analyses captured the underlying temporal trends in potential squid habitat in response to environmental changes transpiring at each climatic transition, regulated by phase shifts in Pacific decadal oscillation (PDO) from 1999–2013. The spatial differences in environmental conditions were apparent across transitions and presumably modulate the local changes in suitable squid habitat over time. Specifically, during a cold to warm PDO shift, decreases in the summer potential habitat (mean rate ± standard deviation: −0.04 ± 0.02 habitat suitability index (HSI)/yr) were observed along the southern edge of the subarctic frontal zone (162°E–172°W). Coincidentally, this area also exhibits a warming trend (mean temporal trend: 0.06 ± 0.21 °C/yr), accompanied with the prevalence of cold-core mesoscale eddies, west of the dateline (mean temporal trend in sea surface height: −0.19 ± 1.05 cm/yr). These conditions potentially generate less favorable foraging habitat for squid. However, a warm-to-cold PDO transition underpins a northward shift of suitable habitat and an eastward shift of regions exhibiting the highest rate of potential squid habitat loss (170–160°W; mean temporal trend: −0.05 ± 0.03 HSI/yr). Nonetheless, the emergence of the areas with increasingly suitable habitat regardless of climate transitions suggests the ecological importance of these regions as potential squid habitat hotspots and climatic refugia. [ABSTRACT FROM AUTHOR]

The size structure of the phytoplankton community strongly affects energy flow through food webs; hence, monitoring the spatial and temporal dynamics of phytoplankton size structure is crucial to evaluate variability in marine ecosystems. In this study, the spatiotemporal changes in phytoplankton size structure and their impact on benthic macrofaunal distribution were examined in the Pacific Arctic as part of the international Distributed Biological Observatory effort. The exponent of the chlorophyll- a (Chl a) size distribution (hereafter, CSD slope), which is an index of synoptic size structure of a phytoplankton community, was estimated based on spectral shape of the phytoplankton absorption coefficient using satellite ocean color data. The CSD slope during the post-bloom period was significantly correlated with sediment Chl a concentration, suggesting that the amount of organic carbon input to the seafloor was strongly related to surface phytoplankton size structure after the spring bloom. Average macrofaunal biomass in the Pacific Arctic was persistently high (>20 g C m−2) throughout 2000–2013 in the regional hotspots, and the biomass-based latitudinal centroid of macrofaunal habitat in the region shifted significantly (p < 0.05) northward. This northward shift is likely driven by a spatiotemporal change in phytoplankton size structure during the post-bloom period. Our results suggest that bottom-up forcing by the phytoplankton community affected the distribution of benthic macrofauna. We conclude that the remote estimate of phytoplankton size structure largely contributes to advancing our knowledge of ecosystem changes observed in the Pacific Arctic marine ecosystem. [ABSTRACT FROM AUTHOR]