The trophic position of the Atlantic blue crab Callinectes sapidus Rathbun 1896 in the food web of Parila Lagoon (South Eastern Adriatic, Croatia): a first assessment using stable isotopes.

Abstract

The Atlantic blue crab Callinectes sapidus is to date widely distributed in the Mediterranean Sea, where is recognized as an Invasive Alien Species. Noticeably, while records of its occurrence are increasing, quantitative information on its functional role in the benthic food webs of invaded coastal habitats are scarce.Here, carbon and nitrogen isotopic signatures were measured in C. sapidus and other representative taxa of the benthic flora and fauna sampled in summer in the Parila Lagoon, a coastal basin located in the Neretva River estuary area (Croatia). d15N values of individual blue crab specimens were used to calculate their trophic position (TP) , using the filter feeder mussel Mytilus galloprovincialis as the isotopic baseline. In general, the isotopic signature of C. sapidus was comparable with those characterizing invertebrate and fish predators (e.g., Hexaplex trunculus, Gobius niger). An average trophic position of 3.73 was estimated for the blue crab population. However, a considerable inter-individual variation was observed in TP values, significantly related with the size of the specimens. Interestingly, a hump-shaped quadratic polynomial resulted the best fitting model for the data, characterized for small-size individuals by a positive body size-TP relationship, leveling or even turning negative for larger adult crabs. The interplay between environmental factors and ontogenetic diet shifts in determining the trophic position of the blue crab and, ultimately, its ecological impact on the benthic community of the Parila Lagoon is discussed.

Is the Kornati National Park Still an Acceptable Reference Area for Environmental Studies?

“…The measured δ 15 N values of H. trunculus in the present study (+8.87 to +10.4 ) are in the same range of values as those determined by Cresson et al [2], Mancinelli et al [29], and Erdelez [31], reporting average values of +8.69 , approximately +12 , and +9.89 , respectively. Marić [32] reported slightly lower values (+6.8 to +7.0 ).…”

“…H. trunculus is an opportunistic and generalist predator, which includes invertebrates into its diet but excludes plant material [29,30]. Even though H. trunculus is one of the most common organisms in the Mediterranean Sea, not many studies on isotope fingerprints related to it have been published.…”

“…The positive δ 15 N values of H. trunculus are typical of its predatory feeding behavior, as is the presence of the pigments indirubin (C 16 H 10 O 2 N 2 ), indigotin (C 16 H 8 N 2 Na 2 O 8 S 2 ), and other mono-and dibrominated derivatives, which are formed in the glands of this organism [13,29]. Surowiec et al [13] have proved the presence of the pigment indirubin (C 16 H 10 O 2 N 2 ) in the glands of H. trunculus, where compounds substituted one CO group with a CNH group [13].…”

Population Dynamics and Reproduction of Mediterranean Green Crab Carcinus aestuarii in Parila Lagoon (Neretva Estuary, Adriatic Sea, Croatia) as Fishery Management Tools

“…The good ecological status and function of the lagoon is of crucial importance for many species targeted by artisanal fishery (Bartulović et al 2006; L. and to the socioeconomy of the area (Glamuzina 2010). However, the lagoon currently suffers from several impacts, including biological invasions (e.g., the Atlantic blue crab Callinectes sapidus [Onofri et al 2008;Dulčić et al 2011;Mancinelli et al 2016]) and anomalous water temperature rises in summer (Sarà et al 2014). Management and monitoring actions of the Parila Lagoon, as well as of other transitional ecosystems, are complex and costly, requiring the development of biological indicators effective in assessing the current ecological status, indicative of the underlying causes of environmental change and suggestive of future environmental changes (Van Den Broeck et al 2015).…”

“…The species is known to play an important role in native coastal ecosystems due to its value as a food item for several high-market-value fish species, such as Gilthead Seabream Sparus aurata, European Sea Bass Dicentrarchus labrax, and European Eel Anguilla anguilla (Mori et al 1990;Özbek et al 2012). Based on its diet, the species exhibits a rather high trophic level value in invaded ecosystems of 3.43 ± 0.35 (adults; Chen et al 2004), similar to native ecosystems, such as 3.63 ± 0.11 in Parila Lagoon (Mancinelli et al 2016).…”