Effects of multiple stressors on coastal copepods: MULTICOP

Hvordan påvirker forhøyete kobbernivåer livet i havet, når det også er andre stressorer tilstede? Forurensning er en av dagens mest presserende miljøutfordringer for livet i havet. Forurensende stoffer påvirker dyrene i havet sammen med naturlige stressfaktorer som predasjon og sult. I vårt prosjekt MULTICOP - Effekter av flere stressfaktorer på kystlevende hoppekreps -, studerer vi effektene av kombinerte abiotiske, biotiske og menneskeskapte stressfaktorer på biologiske responser hos viktige sjølevende dyreplankton; hoppekreps. Disse små krepsdyrene er avgjørende for funksjonen til det marine næringsnettet, da de er en viktig matkilde for fisk. Vi kombinerte laboratorie-, felt- og modelleringsstudier av hoppekreps for å identifisere hvordan opplevd risiko for å bli spist endrer giftighetsresponsen på et vanlig metall når konsentrasjonen er forhøyet og overstiger nødvendige lave verdier. Vi bruker lukten av trepigget stingsild for å simulere predasjonsrisiko, og kobber som modell for vårt forurensende stoff. Kobber er et mye og økende brukt antibegroings-biocid langs den norske kysten. En analyse av publisert litteratur viste oss at en av de største fysiske driverne for kobbergiftighet er temperatur. Imidlertid er det lite kjent hvordan biologiske stressfaktorer påvirker kobbergiftigheten. Kobber reduserte reproduksjonsraten til hoppekreps, som er en av de viktige bidragsyterne til populasjonsvekst. Når hoppekreps oppfatter rovdyr, formerer de seg raskere, men ikke nok til å kompensere for den lavere reproduksjonsraten forårsaket av kobber. Kobber reduserer også antall egg som klekkes. Vi sjekket overlevelsen til forskjellige hoppekrepsarter og fant at økt kobberkonsentrasjon reduserte overlevelsen for alle. Men med samtidig risiko for å bli spist var hoppekrepsene imidlertid mindre følsomme for kobber. Generelt har forskjellige hoppekrepsarter forskjellig følsomhet for kobber. Noen blir lettere påvirket enn andre, og yngre stadier er vanligvis mer sårbare enn voksne. I et feltforsøk som gikk over en hel sommersesong og flere generasjoner, fant vi at til tross for de tilsynelatende positive effektene av rovdyrs tilstedeværelse på overlevelse, hadde kombinert stress fra kobber og rovdyr en negativ effekt på antallet hoppekreps. Andre arter, som ikke-bitende mygg, klarte seg bra til tross for kombinert stress. Da vi testet følsomheten hos hoppekreps fra en fjord med historisk kobbereksponering, så vi ingen åpenbare tegn på at de var tilpasset de tidligere høye kobbernivåene. I motsetning til forventningene, kan rovdyr få hoppekreps til å produsere mer av en naturlig substans kalt astaxantin, et antioksidantpigment, mens kobber ser ut til å redusere mengden av denne substansen. Vi fant også at høyere temperaturer gjorde kobber mer giftig for hoppekreps, mens vannets saltholdighet ikke så ut til å endre kobbergiftigheten. Studien vår understreker den presserende nødvendigheten av å takle utfordringene marine organismer som hoppekreps står overfor når de blir utsatt for flere samtidige miljøbelastninger. Den tjener som en påminnelse om de potensielle konsekvensene av forurensning og andre stressfaktorer på våre marine økosystemer.

In MULTICOP, we found that the effects of multiple stressors on organisms are complex and difficult to predict in detail, as they are context dependent. Specifically, we show that effects of excess copper depend on the organism’s natural environment, including abiotic factors such as temperature, and biological factors such as predation risk (risk of being eaten). In the broader context, this implies that the current managemental approval process for biocides and their effect threshold levels, which are determined by testing contaminants under constant and optimal condition, needs to be updated to include interactions between contaminants and their environment. Examples of increased knowledge regarding the limitations of the current environmental risk assessments are that: • toxicity of copper varies depending on taxonomic diversity, even within a group of the small but important crustaceans, the copepods. • toxicity of copper depends on environmental factors such as temperature and the presence of other stressors such as predation risk. • even in a stressful environment such as a tidal splash pool, the toxic effect of excess copper is clear despite extreme variations in temperatures and salinities. We have contributed to the education and development of expertise in the field of ecotoxicology with three successful master students (Trym R. Dingstad; Solveig Brochmann; Hilde Bruserud). All have been since been recruited into relevant jobs in the research and environmental management. We have further developed the research capacity by: • One post doctor (Torben Lode) and researcher (Jan Heuschele) who have fulfilled and increased their qualifications by scientific work, publications, supervision of supervisors, leading the lab, and contact with end-users, in addition to work with data management and contribution to the data management plan. • The post doctor now holds a permanent research position at The Norwegian Water Resources and Energy Directorate (NVE), and the researcher has continued as a researcher on another RCN project at the section for Aquatic Biology and Toxicology at the Department of Bioscience, University of Oslo. Throughout the project, plans and results were discussed with the stakeholders Miljødirektoratet, Fiskeridirektoratet, Statsforvaltaren i Rogaland, and Havforskningsinstituttet to ensure that results can be used to improve environmental management and risk assessments, as we show that the sensitivity to copper exposure is context dependent. The results are very relevant for the UN Sustainable Development Goals, particularly SdG 14 Life under water. MULTICOP results are also relevant to the broader public since humans and other animal groups are likely to be affected by the combined and interactive effects of contaminants and their environments. The children’s book “Ikke stress meg” will visualize the challenge for young children and their parents and increase the public environmental awareness.

MULTICOP study effects of combined biotic and anthropogenic stressors on key biological responses in important marine animals; the copepods. Coastal waters represent highly relevant biological systems for studying combined effects of biotic stressors on contaminant toxicity. Predation risk importantly structure marine ecosystem dynamics (e.g. diel vertical migration), yet only one marine study exists in which effects of perceived predation risk on anthropogenic stressor toxicity is examined experimentally. MULTICOP takes an integrative approach, combining lab, field and modelling studies, to identify the mechanism by which perceived predation risk potentiates the toxicity response to copper exposure in the coastal copepod Tigriopus brevicornis. Tigriopus spp. occur worldwide and are well established model species in ecotoxicology. Predation risk is simulated by three-spined stickleback kairomones (i.e. chemical cues). Copper is an antifouling biocide used in high volume in shipping and aquaculture along the Norwegian coast. The main approaches of MULTICOP are i) experimental work on individual-level traits to identify effects and mechanisms of combined predation risk and copper exposure, ii) to increase ecological relevance of findings by conducting a species sensitivity distribution (SSD) and by identifying effects of multigenerational exposure on alleviating effects, iii) use dynamic energy budget modelling to identify mechanism of stressor interactions and coupled with population modelling predict population-level consequences of exposure, iv) show from a societal-relevant perspective the importance of considering multiple stressors for environmental monitoring purposes, and v) report results in ways applicable for relevant stakeholders. The MULTICOP results will have important societal impact and provide urgently needed knowledge of biological impacts from multiple stressors with importance to future marine environmental management and sea food production.