Abstract
Alterations of species phenology in response to climate change are now unquestionable. Until now, most studies have reported precocious occurrence of life cycle events as a major phenological response. Desynchronizations of biotic interactions, in particular predator-prey relationships, are however assumed to strongly impact ecosystems’ functioning, as formalized by the Match-Mismatch Hypothesis (MMH). Temporal synchronicity between juvenile fish and zooplankton in estuaries is therefore of essential interest since estuaries are major nursery grounds for many commercial fish species. The Gironde estuary (SW France) has suffered significant alterations over the last three decades, including two Abrupt Ecosystem Shifts (AES), and three contrasted intershift periods. The main objective of this study was to depict modifications in fish and zooplankton phenology among inter-shift periods and discuss the potential effects of the resulting mismatches at a community scale. A flexible Bayesian method was used to estimate and compare yearly patterns of species abundance in the estuary among the three pre-defined periods. Results highlighted (1) an earlier peak of zooplankton production and entrance of fish species in the estuary and (2) a decrease in residence time of both groups in the estuary. Such species-specific phenological changes led to changes in temporal overlap between juvenile fish and their zooplanktonic prey. This situation questions the efficiency and potentially the viability of nursery function of the Gironde estuary, with potential implications for coastal marine fisheries of the Bay of Biscay.
Highlights
Over the last few decades, many authors have reported ongoing biological effects of climate change [1,2,3,4,5,6] impacting species and their habitats and shaping the structure of ecological communities as well as overall functioning of ecosystems [1,7,8,9,10]Among those effects, alterations of species phenology are assumed to have major consequences on ecosystems [3,11]
Our study examined the evolution of phenological patterns for juveniles of several fish species and their prey in the changing climatic and hydrological environment of the Gironde estuary
The present study confirmed that coastal and estuarine ecosystems can be heavily impacted by global change, affecting the structure of biological communities and ecological patterns and phenology
Summary
Over the last few decades, many authors have reported ongoing biological effects of climate change [1,2,3,4,5,6] impacting species and their habitats and shaping the structure of ecological communities as well as overall functioning of ecosystems [1,7,8,9,10]Among those effects, alterations of species phenology are assumed to have major consequences on ecosystems [3,11]. Over the last few decades, many authors have reported ongoing biological effects of climate change [1,2,3,4,5,6] impacting species and their habitats and shaping the structure of ecological communities as well as overall functioning of ecosystems [1,7,8,9,10]. Until now, most studies have reported precocious occurrence of life cycle events as a response to climate change and temperature rise [6,17,18,19], either because of earlier favorable environmental conditions [see exemple of producers in 20,21] or because of phenological modifications in preys or predators dynamics [22]. An increase in time-lag between predator and prey dynamics (occurrence and/or abundance) can lead to socalled mismatches described in the framework of the Match-mis Match Hypothesis (MMH) [23]
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