Gulf of Trieste: A changing ecosystem

Abstract

[1] Understanding the impact of climate change on zooplankton populations is of major importance, as they represent the basis for higher trophic levels in the marine food web. In this study we analyze the 36-year copepod abundance time series in the Gulf of Trieste, northern Adriatic, to investigate its interannual variability, with particular attention to species trends and phenology. Following the analysis of the local winter sea surface temperature, two periods are identified : 1970-1987 and 1988-2005. These periods are characterized by ecosystem-wide changes: an approximate doubling in total copepod abundance, the arrival of a new species (Diaixis pygmoea), the rise (Paracalanus parvus, Oncaea spp., Oithona spp., and Euterpina acutifrons) or decline (Pseudocalanus elongatus, Clausocalanus spp.) of several taxa, and changes in the phenology in several species, with predominantly forward shifts in the timing of the maximum peak. While Acartia clausi remains the dominant species, there is a general trend toward smaller species in the second period. Our results also indicate the large, possibly critical, reduction in the abundance of the species Pseudocalanus elongatus. We hypothesize that the changes in copepod abundances and community composition in the Gulf of Trieste are related to the general warming in the sea surface temperature and associated northerly displacement of the ecosystem and to the changes in the Mediterranean circulation that began at the end of the 1980s and affected the whole basin in the following years as part of the phenomenon called the Eastern Mediterranean Transient.

Feeding of European pilchard (<em>Sardina pilchardus</em>) in the northwestern Mediterranean: from late larvae to adults

“…An obvious effect of such a decrease on the trophic dynamics of sardine in the region is that sardine would be forced to rely more heavily on primary producers as food. In addition, Conversi et al (2009) claimed that species of small copepods would most likely increase as a result of the anticipated warming of the Mediterranean Sea. This increase would impose additional limits on the expansion of phytoplankton species.…”

Long term trends in the sea surface temperature of the Black Sea

“…However, there is an increasing appreciation that current climate change can trigger a major response in the structure and function of marine ecosystems on a decadal timescale, as has been observed in various parts of Correspondence to: G. I. Shapiro (gshapiro@plymouth.ac.uk) the World ocean including the North Atlantic and the North Sea (Reid et al, 2001) and the Mediterranean Sea (Conversi et al, 2009). Recent research demonstrates that changes in temperature, wind and river run-off may also play a role in changes of the Black Sea ecosystem (Daskalov, 2003;Oguz, 2005).…”

Exploring Relationships between Demersal Resources and Environmental Factors in the Ionian Sea (Central Mediterranean)

“…The existence of positive relationships between ecological processes in the sea and NAO was observed in many studies, even though the underlying mechanisms often remain unexplained ( [18 The effects at the first levels of the trophic chain, that is on very short-lived species, are probably easier to identify ([18, and references therein] [25,68]) while those on fish and other high-trophic level organisms are far from being well understood. In the Mediterranean, Lloret et al [72] reported that the recruitment of continental shelf species, among which, E. cirrhosa, M. merluccius, and M. poutassou, was positively correlated with the river run-off and/or wind mixing index.…”

“…The regime shift recorded at the end of the 1980s has had direct effects on several marine ecosystem components encompassing more trophic levels and different Mediterranean basins (see [11,18], and references therein [19,24,25,49,50]). The environmental change observed in the Ionian Sea at the end of 1980s could have affected recruitment directly, through its effects on the survival rate of individuals from eggs to juveniles, or indirectly, through bottom-up effects of the changes in zooplanktonic species [51].…”

“…In particular, changes in the standing stock of the autotrophic biomass and zooplankton abundance with consequent changes in the pelagic community structure were detected in both the Ionian Sea [21][22][23][24] and Adriatic and Ligurian seas [18,19,25]. The inversion of the surface currents in the Ionian Sea was also thought to influence the occurrence of species in the Adriatic Sea, including the first record of the scleractinian coral Astroides calycularis and the teleost fish Sparisoma cretense in this basin [26].…”