Abstract
In this study, we investigated, for the first time, the potential impact of environmental changes on zooplankton abundance over a fourteen year period (2000–2013) at an offshore station in the Eastern Mediterranean Sea (the Levantine basin, offshore Lebanon). Samples were collected monthly and analyzed using the semi-automated system ZooScan. Salinity, temperature and phytoplankton abundance (nano and microphytoplankton) were also measured. Results show no significant temporal trend in sea surface temperature over the years. Between 2005–2010, salinity in the upper layer (0–80 m) of the Levantine basin increased (~0.3°C). During this 5 year period, total zooplankton abundance significantly increased. These modifications were concomitant to the activation of Aegean Sea as a source of dense water formation as part of the “Eastern Mediterranean Transient-like” event. The results of the present study suggested that zooplankton benefited from enhanced phytoplankton production during the mixing years of the event. Changes in the phenology of some taxa were observed accordingly with a predominantly advanced peak of zooplankton abundance. In conclusion, long-term changes in zooplankton abundance were related to the Levantine thermohaline circulation rather than sea surface warming. Sampling must be maintained to assess the impact of long-term climate change on zooplankton communities.
Highlights
Zooplankton communities are crucial components of marine ecosystems due to their central role in marine trophic food webs and their impact on carbon cycling [1]
Our results didn’t appear to confirm earlier studies that showed that global warming caused the rise of the sea surface temperature in the EMed
The most striking result was the clear salinity increase in the upper 80 m of the water column between 2005 and 2010, from 39.05 to 39.35. The timing of this salinity anomaly was consistent with previous studies in the middle of the 2000s in the upper/intermediate layers in the EMed [38], in the easternmost Levantine basin [40] and in the intermediate and deep layers in the Cretan Sea [39]
Summary
Zooplankton communities are crucial components of marine ecosystems due to their central role in marine trophic food webs and their impact on carbon cycling [1]. Zooplankton communities are sensitive to climate change [2] and vulnerable to changes in the hydrography [3]. They are able to respond rapidly to any ecosystem variability [4, 5]. Temporal Variability of Zooplankton (2000-2013) in the Levantine Sea. Chair National Council for Scientific Research/ University Pierre et Marie Curie VISION: LS. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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