Abstract
AbstractFinfish abundance indices, produced from seasonal trawl survey data collected in Long Island Sound, were examined for changes in community composition related to the dynamics of water temperature from 1984 to 2008. In general, seasonal mean catch of species identified a priori as cold adapted significantly decreased while warm‐adapted and subtropical species significantly increased over the time series. Bottom water temperature also significantly increased. As a group, annual abundance of cold‐adapted species exhibited significant negative correlation with mean bottom water temperatures while warm‐adapted species, but not subtropical species, exhibited significant positive correlation. Multivariate analyses identified a shift in community structure producing two primary year‐groupings. Spring groupings were clearly delineated as 1984–1998 (cold period) and 1999–2008 (warm period). Autumn groupings were temporally discontinuous in the 1990s with group membership shifting between cold and warm periods, although the distal ends of the time series were clearly divided. These patterns aligned with deviations from the 1984 to 2008 mean bottom water temperature, indicating that this estuary is experiencing a relatively rapid shift consistent with a response to climate warming. The more distinct delineation of community structure in spring suggests that the lack of advantageous spring conditions was a more important factor in the decline of cold‐adapted species than increasingly stressful conditions in autumn.Received August 30, 2011; accepted April 7, 2012
Highlights
Climate change is a global phenomenon, but the expression of climate-driven changes to regional ecosystems are not uniform, different systems and their component communities experience these effects at differing rates and extent (Solomon et al 2007)
In this study we have examined trends in the Long Island Sound (LIS) finfish community based on data collected in a spatially comprehensive standardized trawl survey conducted over a 25-year time period
The LIS finfish community has shifted from one in which cold-adapted species dominate in spring and warm-adapted species dominate in fall, to one in which warm-adapted species are increasingly abundant in both seasons
Summary
Climate change is a global phenomenon, but the expression of climate-driven changes to regional ecosystems are not uniform, different systems and their component communities experience these effects at differing rates and extent (Solomon et al 2007). Long Island Sound (LIS) is a large semienclosed estuary in the midlatitude Virginian biogeographic region of the northwestern Atlantic Ocean(Briggs 1974; Wolfe et al 1991) This region is a component of the larger Eastern Temperate. Some researchers have identified two subprovinces within the Warm Temperate (i.e., the Virginian, from Cape Cod to Cape Hatteras, and the Carolinian, from Cape Hatteras to Cape Canaveral) and described the Virginian subprovince as a transition zone lacking a unique fauna of its own (Coomans 1962) This level of inconsistency in describing the region’s biogeography is based in part on diverse patterns and dynamics of faunal distributions and in part driven by the wide variation in environmental conditions found across the continental shelf and within the coastal regions in particular (Longhurst 1998; Cook and Auster 2007; Friedland and Hare 2007). Trends in community composition and species abundance were compared to patterns in water temperature to determine if there were significant changes over time and if such changes are indicative of larger-scale changes in thermal regime
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