Effect of an exceptional rainfall event on the sea urchin (Paracentrotus lividus) stock and seagrass distribution in a Mediterranean coastal lagoon

Abstract

A shallow Mediterranean brackish lagoon (Urbinu, Corsica), 700 ha in surface area, characterized by low freshwater input and permanent communication with the open sea, and therefore by relatively stable salinity (usually 30e38), was subject in late 1993 to an exceptional rainfall event occurring on an average once every 50 years: 450 mm in 48 h (compared to the average annual precipitation of 650 mm). The volume of freshwater that poured into the lagoon corresponds to 36% of its volume. As a result, salinity dramatically dropped while turbidity increased. The seagrass Cymodocea nodosa and other habitats were mapped before (1990) and after (1994, 1996, 1999) the rainfall event, and the sea urchin Paracentrotus lividus stock was estimated together with its population structure. In 1994, after the rainfall event, the surface area of seagrass meadows moderately declined, but it cannot be ruled out that this loss may be within their usual inter-annual fluctuations. The sea urchin stock dropped by 50% (6e3 million individuals). Low salinity, turbidity and siltation were probably the reasons for the changes in sea urchin population in addition to variability of dynamic population parameters (e.g. recruitment, mortality). The recovery of sea urchin stock was completed within a few years (six years or less). The high population dynamics and the high recruitment potential of sea urchins may act as a mechanism to maintain sea urchin populations in this highly variable habitat. These results reflect the resilience and high adjustment stability of the system.

Life-history trade-offs and limitations associated with phenotypic adaptation under future ocean warming and elevated salinity

“…Temperature and salinity are among the most important environmental factors that govern the physiology of marine organisms and ultimately determine their geographical distribution [62,63]. Here, we observed that juvenile polychaetes, O. labronica, exhibit increased growth rates under T, which is a common response to warming in marine ectotherms [64].…”

Long-distance electron transport occurs globally in marine sediments

“…The coastal lagoon has a high salinity (∼ 40 at the time of sampling, typically 30-38; Fernandez et al, 2006). The sediment was kept in oxygenated water in a container until it returns to the home laboratory in the Netherlands.…”

Influence of Winter Storms on the Sea Urchin Pathogen Assemblages

“…The spread of these diseases has been associated with extremes in environmental conditions, such as storms and sea temperature increases, which synergistically facilitate the dispersion of pathogenic agents thus causing an increase in their presence in the ecosystems over the last several years because of the global warming (Tajimaa et al, 2007;Feehan et al, 2012). Because sea urchins are key herbivores in the benthic communities, any density-related changes could introduce a risk for the stability and the structure of the benthic ecosystems and generate an impact throughout trophic cascade processes (Fernandez et al, 2006;Clemente et al, 2014;Trowbridge et al, 2019). In the East Atlantic Ocean, two mass mortality events have been reported, one after the storms Xynthia in February 2010 and one after Emma in February 2018 (Hernández et al, 2020) that affected the sea urchin Diadema africanum.…”