Phenological shifts of three interacting zooplankton groups in relation to climate change

Merja Schlüter (1) , Agostino Merico , Marcel Reginatto , Maarten Boersma , Karen Wiltshire , Wulf Greve

1 Ecosystem modeling

Over the past decades, global warming has been linked to shifts in the distributions and abundances of species. In the southern North Sea, temperatures have increased in the last three decades and this will likely have consequences on the seasonality of marine organisms living in the area. Ctenophores such as Beroe gracilis and Pleurobrachia pileus could be particularly affected by changes in their phenology and that of their prey, thus causing shifts in ecosystem function. Despite their global relevance, only a few long-term records of ctenophore abundance exist, and most of these records are semi-quantitative in nature. Therefore, our knowledge of the influence of environmental factors on their population development is limited. The long-term abundance dynamics of Beroe gracilis, Pleurobrachia pileus and their food calanoid copepods were analysed and special attention was focused on the response of these organisms to climate warming. Bayesian statistics showed that the phenology of the two ctenophores shifted in a step-like mode in the year 1987/88 to permanent earlier appearances. The seasonal change in the population blooms of Pleurobrachia pileus and Beroe gracilis correlated with a step-like increase in winter and spring sea surface temperatures. Possible explanations for the changes observed in these organisms could include higher reproductive rates, increased winter survival rates or both. Interannual variations in ctenophore abundances correlated well with the interannual changes in spring temperatures, although the impact of temperature on Beroe gracilis was less pronounced. The changes in copepods abundance were not consistent with changes in Pleurobrachia pileus and Beroe gracilis. Pleurobrachia pileus showed longer periods of high abundance after the permanent seasonal advancement. The longer periods were correlated with a decline in the average autumn abundance of copepods. The extended annual presence of Pleurobrachia pileus could have influenced fish stock decreases observed in the region.

Mots clés: Life Sciences

Merja Schlüter, Agostino Merico, Marcel Reginatto, Maarten Boersma, Karen Wiltshire, et al.. Phenological shifts of three interacting zooplankton groups in relation to climate change. Global Change Biology, 2010, ⟨10.1111/j.1365-2486.2010.02246.x⟩. ⟨hal-00552621⟩