Phytoplankton biodiversity and NW Mediterranean Sea warming: changes in the dinoflagellate genus Ceratium in the 20th century

Abstract

Our knowledge of the response of phytoplankton to climate change is restricted by the lack of phytoplankton long-term studies, especially those reporting species data. To circumvent this problem, we combined recent data from sampling at monitoring sites with old bibliographic data. The study was conducted on the genus Ceratium (planktonic dinoflagellates) in the NW Mediterranean, as numerous studies have been conducted in the area since the beginning of the 20th century. In addition, species of this highly diverse genus are known to be particularly sensitive to water temperature, and should thus be responsive to global warming. The temporal distribution of Ceratium species over the last century showed a progressive disappearance from the surface layer of likely stenothermic species, which may have moved to deeper layers in response to water warming, along with a decrease of species richness during the annual cycle. Seasonal and phenological aspects of Ceratium assemblages were also affected, as illustrated by the earlier timing in the minimum of richness. A change in the overall species assemblage also occurred from past to present in the Ligurian Sea, suggesting a warming in this area consistent with the development in surface water temperatures. Our results suggest that Ceratium species may constitute good biological indicators of warming in the NW Mediterranean Sea. In addition, the present study showed the importance of time-series data and the value of historical literature as the basis for ecological studies of long-term trends needed to substantiate our current understanding of the impact of global change on marine biodiversity. KEY WORDS: Ceratium · Phytoplankton · Climate change · Long-term series · Mediterranean · Biodiversity · Biological indicator · Historical ecology Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 375: [85][86][87][88][89][90][91][92][93][94][95][96][97][98][99] 2009 Gentili 1996, Johnson 1997, Marbà & Duarte 1997, although periodic patterns such as the 22 to 25 yr period of solar activity may overlay the monotonic trends and mask them (Duarte et al. 1999). Nutrient concentrations, particularly phosphate and nitrogen, have also increased from the early 1960s, probably due to increasing atmospheric and terrestrial inputs, while concentration in silicate has remained relatively constant (Béthoux et al. 2002).Using different approaches, a number of studies have provided information on the temporal distribution of Mediterranean Sea phytoplankton (Duarte et al. 1999, Goffart et al. 2002, Marty et al. 2002, Gómez & Gorsky 2003, Bosc et al. 2004, Ribera d'Alcalà et al. 2004. Some of these studies show changes in phytoplankton in the NW Mediterranean in relation to climatic forcing. Pigment analysis over a decade revealed a positive trend in phytoplankton biomass in response to the lengthening of the summer stratification, accompanied by an increase of small-sized phytoplankton (picoplankton and nanoflagellates) able to support re...

Temperature effects on the heterotrophic bacteria, heterotrophic nanoflagellates, and microbial top predators of the NW Mediterranean

“…Similarly, warming increased the abundance of ciliates and decreased the development time of copepods in mesocosms deployed in the Thau Lagoon (Vidussi et al 2011). Over longer periods of time (within the last 100 yr), warmer sea surface temperatures changed the community composition of the Ceratium genus in Villefranche Bay due to the disappearance of some stenotherm species (Tunin-Ley et al 2009). Laboratory experiments have shown that a small increase in temperature per generation time (0.1 to 0.2°C) may increase the risk of extinction of herbivorous protists, and microbial communities may become dominated by bacterivores (Petchey et al 1999).…”

New evidence links changing shelf phytoplankton communities to boundary currents in southeast Tasmania

“…The Ceratium species are known from warm waters of the Tasman Sea (Hallegraeff et al 2010) and, considering the season, we suggest that the strengthening EAC was responsible for their appearance in southern Tasmania. The poleward extension of tropical and warmtemperate Ceratium species has been well documented in the Northern Hemisphere (Dodge and Marshall 1994;Johns et al 2003;Barnard et al 2004;Hays et al 2005;Edwards et al 2006), and it is predicted that subsequent expansions will occur into the future (Turin-Ley et al 2009). As Tasmania is expected to experience continued ocean warming into this century (Ridgway and Hill 2009), it follows that introductions of Ceratium, and perhaps other warm water species, will also be observed.…”

“…It is acknowledged that species of Ceratium may exert a seasonal competitive advantage over other microphytoplankton, as they are able to tolerate a wide range of environmental conditions (Baek et al 2007). Some studies suggest that a mixotrophic feeding strategy contributes to a competitive advantage (Mikaelyan and Zavyalova 1999; Smalley et al 1999;Turin-Ley et al 2009), allowing Ceratium species to overcome nutrient depleted waters above the thermocline and light depleted waters below the thermocline. Others highlight Ceratium as a poor food option for most species of grazing zooplankton due to their large size (Graneli et al 1989) and characteristic shapes (Hargrave and Geen 1970).…”

“…The creation of mixed communities and transitional zones are common impacts of changing oceanographic conditions. Research focussing on the biological implications stemming from the presence of warm-water species in cooler regions highlights possible declines in coolwater species (Scavia et al 2002;Beaugrand 2004;Turin-Ley et al 2009;Johnson et al 2011), declines in overall plankton diversity (Johns et al 2003;TurinLey et al 2009) and the potential reorganisation of plankton phenology, community structure and abundance (Hays et al 2005;Turin-Ley et al 2009). Regarding Tasmania specifically, Johnson et al (2011) suggests that population-level changes to commercially important invertebrates, such as abalone and rock lobster stocks, are of concern as Tasmanian plankton communities are modified.…”

Dinoflagellate Ceratium symmetricum Pavillard (Gonyaulacales: Ceratiaceae): Its occurrence in the Hooghly-Matla Estuary and offshore of Indian Sundarban and its significance

“…Ceratium Schrank, an armoured dinoflagellate genus has been considered a biological model for a wide range of studies as utilized by TuninLey et al (2007TuninLey et al ( , 2009. One of the several advantages offered by this genus is that identification of species level is more feasible than other phytoplankton group (Tunin-Ley et al 2009). Apart from this, Ceratium is known for its sensitivity to temperature in terms of biogeography (Dodge & Marshall 1994), seasonality and morphology (Sournia 1967).…”