Detrimental physiological effects of the invasive alga Caulerpa racemosa on the Mediterranean white seabream Diplodus sargus

Abstract

Observational data suggest that the white seabream Diplodus sargus, a sparid fish of economic and ecological relevance in the Mediterranean Sea, has included the invasive green alga Caulerpa racemosa in its diet. Here we adopted a chemoecological approach to study the trophic relationship between the fish and the exotic pest. We demonstrated that the red pigment caulerpin, the most abundant secondary metabolite of C. racemosa, enters food chains and accumulates in the fish tissues. General biological condition markers associated with fish health and reproductive development were measured and correlated with the caulerpin levels in the fish tissues. Significant correlations among caulerpin tissue load (determined by liquid chromatography-mass spectrometry analysis) and fish condition factor and hepatosomatic index were obtained, suggesting a possible detrimental effect of the dietary exposure to C. racemosa on D. sargus. Glutathione peroxidase and catalase activity were also significantly correlated with caulerpin concentrations in the liver, suggesting a possible interaction between algal metabolites and liver antioxidant mechanisms. Studies on the impact of invasive macroalgae on marine assemblages have been almost exclusively focused on the structural modification of benthic assemblages, through the alteration of the relative importance of some endemic species and the modification of habitat complexity. Here we propose a new mechanism by which invasive algae can impact marine systems, namely the entry of pest metabolites in food webs, with potential detrimental effects on the population dynamics of a single species, alteration of trophic webs and changes in the functioning of coastal ecosystems.

Biomarker Approach in Marine Monitoring and Assessment: New Insights and Perspectives

“…Moreover, in the same studies [50,51] the exposure to the alga was also demonstrated to induce a) alteration of the activity of the Na + -K + -ATPase, which is responsible for the electrochemical gradient across the plasma membrane and it is critical for the osmotic balance of the cell, the resting membrane potential, and the excitable properties of muscle and nerve cells [54][55][56][57][58], b) neurotoxic effects, documented by acetylcholinesterase inhibition, and c) changes in the morphology of gonads. The observed alterations may cause detrimental health status and altered behaviour in the fish, potentially preventing the reproductive success of fish population [51].…”

“…In two recent studies [50,51] carried out along the Apulian coasts (Northern Ionian Sea, SE Italy) the authors found that C. racemosa changes foraging habit of the native white seabream, Diplodus sargus. In invaded areas, a high frequency of occurrence of C. racemosa in the stomach contents of this omnivorous fish was found in parallel with a significant accumulation of caulerpin, one of the main secondary metabolites of C. racemosa, in fish tissues.…”

“…Besides its application in chemical pollution monitoring and assessment, recently the usefulness of the biomarker approach has been demonstrated also for the detection of the impact of alien species in marine environments [50,51]. Alien species can cause severe changes in the ecosystem's functioning and are recently recognized as principal agents of global change [52].…”

Idiosyncratic effects of protection in a remote marine reserve

“…Although both multiple-use MPAs and no-take reserves could indirectly mitigate human impacts by increasing the resilience of protected systems (Bellwood et al 2004, Hughes et al 2005, they cannot directly cope with many external stressors, such as terrestrial pollution, spread of pathogens, climate change and marine invasive species (Halpern et al 2008, Mora & Sale 2011, Terlizzi et al 2011 and they are most useful when embedded into broader, multisector management plans (Fraschetti et al 2011).…”

Seasonal rubisco enzyme activities and caulerpenyne levels in invasive Caulerpa racemosa var. cylindracea and native Caulerpa prolifera

“…Since no valid eradication method has been published on this species, C. racemosa has been continuing its invasion in the Mediterranean Sea. Its effects on the sublittoral ecosystem of the Mediterranean Sea have been mentioned in many reports (Terlizzi et al, 2011;Katsanevakis et al, 2011;Box et al, 2010;Deudero et al, 2010;Klein&Verlaque, 2008). Caulerpa prolifera (Forsskål) J.V.…”