Abstract
Carbon mass of the non-indigenous predatory fishhook water flea Cercopagis pengoi (Ostroumov, 1891) from the eastern Gulf of Finland, the Baltic Sea, was for the first time measured using the high temperature combustion method. Prior to the analysis, individual dry weight of Cercopagis was determined; altogether ca. 500 organisms were examined. Mean individual dry weight of C. pengoi for July-September was estimated as 34.0 µg; carbon mass averaged 15.8 µg; carbon content, calculated as percent of dry weight, averaged 43.4%. Those values varied over months, mainly because of different population structure of C. pengoi and variation in their diet due to seasonal dynamics of the food objects. However, relations between carbon mass and dry weight for different months did not differ statistically (p<0.001). Therefore, the general polynomial regressions (k=2), describing carbon mass-to-dry weight and carbon content-to-dry weight relationships, were calculated for the entire dataset of individual measurements of C. pengoi body metrics. These data will contribute to adequate evaluation of food web structure and ecosystem alterations in various water bodies invaded by C. pengoi which has got a strong potential to pelagic food web transformations that may impact the overall energy balance and decrease the size of fish stocks.
Highlights
In invasion biology, ecosystems vulnerability to non-indigenous species introductions, biodiversity of native communities and competitive resource utilization depending on the size of organisms are pervasive and closely linked to environmental changes (Holopainen et al 2016)
Dry weight of C. pengoi individuals collected in the eastern Gulf of Finland in July– September 1997 ranged one order of magnitude: from 9 to 94 μg; variation in carbon mass exceeded two orders of magnitude and ranged from 0.21 μg to 46.09 μg
The exceptionally low values of Carbon mass (CM) (< 1.0 μg) and the relevant dry weight (DW) and Carbon content (CC) values were excluded from the analyses as possible results of methodological bias during CMmeasurements in the smallest individuals of C. pengoi
Summary
Ecosystems vulnerability to non-indigenous species introductions, biodiversity of native communities and competitive resource utilization depending on the size of organisms are pervasive and closely linked to environmental changes (Holopainen et al 2016). Precise knowledge of the individual carbon mass and carbon content of aquatic organisms is of exceptional value when assessment of the impacts of alien species invasions on the ecosystems, food webs, competitive interactions, and composition of native communities is in the research focus Among such hotspot research fields is the estimation of ecosystem impact of the opportunistic generalist predator – the Ponto-Caspian onychopod cladoceran Cercopagis pengoi (Ostroumov, 1891), one of the recent invaders to the Baltic Sea (Ojaveer and Lumberg 1995, Krylov et al 1999, Leppäkoski et al 2002, Telesh et al 1999, 2001, 2008, Rowe et al 2016) and to the Laurentian Great Lakes (MacIsaac et al 1999, Therriault et al 2002). This invader has got a strong potential to cause alterations in plankton communities, including population shifts (Ojaveer et al 2004, Telesh and Ojaveer 2002), resource competition (Holliland et al 2012, Lehtiniemi and Lindén 2006), depletion of prey populations (Kotta et al 2006), or changes in energy fluxes (Laxson et al 2003, Litvinchuk and Telesh 2006, Naumenko and Telesh 2008)
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