engleski

Going with the flow: nudibranch gastropods track large-scale fluctuations in climate

Climate change is restructuring marine ecosystems worldwide, and an understanding of causal mechanisms is essential for informed forecasting and management. We used climate- index response profiling (CIRP), a novel autoregressive technique applied to multi-year time series of population abundance, to test mechanistic hypotheses about recent marked declines in shallow-water nudibranchs in California. We analyzed historical data of 56 species from three intertidal sites studied independently in central California during non- overlapping time periods between 1969 and 1995, combined with recent resurveys from these same sites. Total abundance, especially of larger more conspicuous species, at each site was generally positively correlated with El Niño conditions, warm phases of the Pacific Decadal Oscillation, elevated local sea level and sea surface temperatures, and negatively correlated with coastal upwelling and the North Pacific Gyre Oscillation. Southern species reflected this overall pattern, but northern species were not as strongly associated with the climate indices, except at Pillar Point where they were correlated in the same direction as the southern species. A random-effects meta- analysis of these results rejected thermal stress and trophic collapse hypotheses, implicating larval advection as the likeliest mechanism linking oceanographic changes with the faunal shifts, and indicating that recent declines are likely to be reversed when El Niño conditions return. CIRP presents a practical and quantitative method for understanding and forecasting population fluctuations of a conspicuous predatory guild in the California Current System.

PDO ; NPGO ; MEI ; ENSO ; El Nino ; nudibranch ; California

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