Evaluation of Paracentrotus lividus (Lamarck, 1816) exotrophic larvae as live feed for marine decapod crustacean larvae

Tese de doutoramento, Biologia (Biologia Marinha e Aquacultura), Universidade de Lisboa, Faculdade de Ciências, 2012In the present study, we have evaluated 4‐arm exotrophic larvae of sea urchin Paracentrotus lividus (Echinodermata: Echinoidea) as live feed in marine decapod crustacean larviculture, in comparison to Artemia spp. naupliar stages, a commonly used live prey in marine hatcheries. We therefore investigated several key parameters to assess the potential of P. lividus plutei as live feed for crustacean larvae, namely: 1) broodstock diet manipulation in order to obtain both quantitative and qualitative year round production of 4‐arm echinoplutei, free from environmental and reproductive seasonal constraints; 2) best possible biotic conditions to perform sea urchin in vitro fertilization, namely sperm:egg ratios and egg concentrations, and its relation to early stage segmentation and larvae development; 3) mass production possibility in terms of larvae media culture conditions, plutei stocking densities and larvae feed and enrichment; and acceptability as live feed by predator larvae (Lysmata seticaudata, Palaemon elegans, Maja brachydactyla, Pachygrapsus marmoratus and Xantho incisus). Additionally, we studied the possibility to differentiate P. lividus broodstock sex by means of a spine external morphological characteristic. Under controlled laboratory conditions, percent egg fertilization above 99% and high values for percent normal development (≥85%) were obtained when captive breed P. lividus broodstock was fed an inert diet based upon maize and wheat flour mixture. Whole egg total amino acid composition was similar between P. lividus fed this inert diet and wild caught organisms. Enrichment potential in terms 4‐arm plutei fatty acid profile and lipid content was possible through manipulation of the lipid source chosen for captive P. lividus broodstock diet. Sperm:egg ratios were found to influence percent egg fertilization and segmentation development after 90 minutes post‐fertilization, but not plutei total length, post‐oral arm length and normal percent larvae development. Water renewal (every 2 days) during P. lividus larviculture was found to be an essential abiotic culture condition to sustain plutei development and survival until 18 days post‐fertilization. All plutei larval feeds (live microalgae, inert microdiets, single or mixed provided), supported P. lividus larvae growth and survival until 18 days post‐fertilization (DPF), with D. tertiolecta being found to be the most appropriate diet in terms of larvae development and survival outcome. When cultured at a initial stocking density of 40 plutei.ml‐1, inert microdiets were unable to sustain P. lividus plutei survival to 10 DPF. Plutei survival was found to be inversely correlated with increasing culture densities. Paracentrotus lividus plutei enrichment with Algamac 3050 flake, was found to cause mass mortality at 5 and 10 DPF. Paracentrotus lividus exotrophic 4‐arm plutei was ingested and preyed by 4 (Lysmata seticaudata, Maja brachydactyla, Pachygrapsus marmoratus and Xantho incisus) out of 5 crustacean larvae tested, but were unable to sustain complete larvae development and survival to settlement of L. seticaudata, M. brachydactyla and P. marmoratus species. No apparent advantage of P. lividus 4‐arm plutei as live feed for marine crustacean decapod larvae was found in comparison to Artemia spp.. Finally, the analysed spine morphological characteristic, as a tool for sex differentiation between P. lividus adults, does not allow accurate and feasible results.Os estudos efectuados e incluídos nesta tese de doutoramento, resultam da formulação de uma hipótese que se baseou em evidências cientificamente comprovadas e que pretendeu a avaliar a utilização de larvas exotróficas do equinoderme Paracentrotus lividus (Lamarck, 1816) (Echinodermata: Echinoidea) como presas vivas na larvicultura de crustáceos decápodes marinhos. No seguimento de evidências científicas baseadas em estudos ao nível de comunidades planctónicas marinhas, que demonstram a importância de estadios larvares de ouriços‐do‐mar na sua composição e biomassa, acrescido de resultados laboratoriais que comprovam a sua predação por estadios larvares de crustáceos marinhos, pretendeu‐se inferir o potencial de larvas exotróficas de P. lividus como presa vivas face a outras espécie zooplanctónica normalmente usada como alimento vivo (Artemia spp.). Neste contexto, efectuou‐se um conjunto de estudos experimentais com o objectivo de verificar a aplicabilidade da hipótese sugerida. Deste modo escolheu‐se esta espécie uma vez que se trata do ouriço‐do‐mar de maior abundância na zona rochosa intertidal e subtidal da costa Portuguesa. Em segundo lugar, informação cientifica disponível permite a manutenção desta espécie em cativeiro, com custos operacionais baixos. De igual modo sendo possível a manutenção anual de organismos adultos maturos em cativeiro, independentemente da época reprodutiva no meio natural, torna possível a obtenção em cativeiro de grandes quantidades de gâmetas e consequentemente de larvas. A escolha de estadios larvares exotróficos prendeu‐se por um lado com o facto da sua biometria ser semelhante a naúplios recém‐eclodidos e metanáuplios (24h) de Artemia spp., assim como à hipótese da sua qualidade nutricional poder ser melhorada por intermédio de alimentação exógena. Finalmente e dada a sua fraca capacidade natatória, estes estadios podem constituir uma presa com maior capacidade de captura por parte de potenciais predadores. De modo a avaliar a potencialidade destas larvas como presas vivas na larvicultura marinha, procedeu‐se a elaboração de um conjunto de trabalhos experimentais, com vista à verificação da hipótese apresentada. Em primeiro lugar foi analisado o efeito da alimentação (dietas naturais e artificiais) de adultos desta espécie em cativeiro ao nível do índice gonadossomático, conteúdo proteico de óvulos (aminoácidos), taxas de fertilização, biometria e desenvolvimento larvar normal. Foi efectuada uma comparação com ouriços‐do mar selvagens, recolhidos durante a época reprodutiva. Obtiveram‐se valores similares de desenvolvimento larvar normal entre organismos selvagens e adultos alimentados com uma das dietas inertes usadas. Como principal resultado ficou provada a possibilidade de obtenção de taxas de desenvolvimento larvar normal elevadas, quando adultos de P. lividus, mantidos em cativeiro, eram alimentados com uma dieta inerte apropriada, cuja fonte proteica é baseada numa mistura de farinha de milho e trigo. De seguida inferiu‐se a qualidade nutricional (conteúdo lipídico e composição em ácidos gordos) de óvulos e larvas endotróficas de P. lividus mantidos em cativeiro e alimentados com dietas naturais (grãos de milho, macrolgas e mistura) e inertes. Procedeuse posteriormente à manipulação lipídica de dietas inertes artificiais, pela incorporação de óleos ricos em ácidos gordos poliinsaturados. Como principal resultado, verificou‐se a incorporação de ácidos gordos poliinsaturados em óvulos e larvas endotróficas resultantes de adultos cuja alimentação tinha sido efectuada com dietas artificiais elaboradas com fontes lípidicas com uma maior proporção de lípidos insaturados. Posteriormente foram investigados quais os efeitos que diferentes racios de espermatozóides:óvulos e concentração de óvulos, aplicados na fertilização in vitro desta espécie, poderiam ter ao nível de taxas de fertilização, desenvolvimento embrionário, biometria e desenvolvimento larvar resultante. Pretendeu‐se deste modo inferir se existia alguma relação directa entre a hipótese formulada e os resultados obtidos, para os parâmetros analisados. Verificou‐se que com o aumento de rácios de espermatozóides:óvulos testados, ocorre um aumento nas percentagens de taxas de fertilização, embriões fertilizados (não desenvolvidos) e embriões segmentados (4 células), contrariamente ao decréscimo observado para embriões em estadio de segmentação de 2 células. De igual modo, verificou‐se um decréscimo nos valores obtidos de desenvolvimento larvar normal e tamanho de braços pós‐orais, com o aumento na concentração de óvulos testadas, o que possivelmente poderá estar relacionado com o aumento de densidades de cultivo larvares. Como principal resultado, racios de espermatozóides:óvulos superiores a 300:1, aparentemente influenciam negativamente a segmentação embrionária normal de P. lividus, mas não a morfogénese de echinopluteus de 4 braços, 72 horas após fertilização. Seguidamente, foram avaliadas e testadas várias condições de cultivo larvar de P. lividus, tendo como objectivo a aferição da possibilidade da sua larvicultura em massa. Foram analisados diversos parâmetros (arejamento, mudança de meio de cultivo, dietas, densidades de cultivo e enriquecimento). Como principal resultado, verificou‐se a obtenção de taxas de sobrevivência superiores a 77.0 %, para larvas exotróficas até 6 dias após fertilização, independentemente das densidades de cultivo testadas. De igual modo, taxas de sobrevivência larvar superiores a 52.9 %, aos 18 dias após fertilização, só foram obtidas quando pluteus foram alimentados com D. tertiolecta, a uma densidade de cultivo inicial de 1.5 pluteus.mL‐1 e sob determinadas condições de cultivo (com arejamento e mudança de meio de cultivo a cada 2 dias). Adicionalmente, verificou‐se no que respeita às dietas testadas, que a microalga D. tertiolecta, foi a alimentação que melhores resultados proporcionou, quer em taxas de sobrevivência larvar, quer na percentagem final de pluteus no estadio de 8 braços, após 18 dias de larvicultura, face a dietas microencapsuladas. Adicionalmente verificou‐se a possibilidade de efectuar o enriquecimento de pluteus aos 5 e 10 dias após fertilização, por intermédio da utilização de um produto comercial (Algamac 3050 flake). Como principal resultado, verificou‐se a obtenção de taxas de mortalidade elevadas em larvas exotróficas de P. lividus (5 e 10 dias após fertilização) após a tentativa de enriquecimento com Algamac 3050 Flake, por um período de 12h. De igual modo, verificouse a possibilidade de produção em massa de pluteus (40 pluteus.mL‐1), até 5 e 10 dias após fertilização, por intermédio da utilização da microalga D. tertiolecta e microdietas artificiais (Frippak 1#CAR e Lanzy spirulina+) como fonte de alimentação larvar, tendo‐se verificado valores de sobrevivência larvar baixos (15,1 % e 11,9 %) aos 5 dias após fertilização e 100% de mortalidade aos 10 dias após fertilização, respectivamente, nas experiências em que as dietas artificiais foram usadas como alimento para as larvas exotróficas. Posteriormente, foram efectuadas uma série de experiências com vista ao estudo do potencial da utilização de larvas exotróficas de P. lividus (4 braços), como alimento vivo na larvicultura de crustáceos decápodes marinhos. Deste modo, foram verificadas em primeiro lugar, taxas de ingestão (24 horas) de 5 potenciais predadores (Lysmata seticaudata, Palaemon elegans, Maja brachydactyla, Pachygrapsus marmoratus e Xantho incisus) face a oito presas vivas (ovócitos; gástrulas; pluteus com 4 braços, com 5 e 10 dias após fertilização; pluteus com 6 seis braços, com 12 dias após fertilização; Pluteus com 8 braços, 18 dias após fertilização; Artemia spp. recém‐eclodida; Artemia spp. 24horas após eclosão). Verificou‐se para as espécies de predadores testadas, que unicamente Lysmata seticaudata, Maja brachydactyla, Pachygrapsus marmoratus e Xantho incisus, consumiam estadios larvares de P. lividus. Lysmata seticaudata foi a espécie de predador que ingeriu todas as presas vivas de entre os predadores testados, tendo mesmo sido a única onde se constatou a ingestão de pluteus com 6 e 8 braços. Posteriormente, foi avaliada o desenvolvimento e sobrevivências larvares das espécies Lysmata seticaudata, Maja brachydactyla e Pachygrapsus marmoratus alimentadas com larvas exotróficas de P. lividus (3 e 5 dias após fertilização) vs. Artemia spp. ao longo do cultivo larvar destes crustáceos. Como resultado principal, verificou‐se que as larvas exotróficas de P. lividus permitiram a sobrevivência e desenvolvimento larvar de L. seticaudata até 28 dias após eclosão e estadio IV; M. brachydactyla até 12 dias após eclosão e estadio II; e P. marmoratus até 9 dias após eclosão, não se tendo observado para esta última espécie, o desenvolvimento larvar além do estadio de zoea I. De igual modo, verificou‐se que os equinopluteus exotróficos usados como presas vivas, não permitiram a obtenção de resultados superiores em termos de desenvolvimento e taxas de sobrevivência larvar dos predadores testados, face a Artemia spp.. Por fim foi analisada a possibilidade da utilização de uma determinada característica morfológica externa dos espinhos de P. lividus, com o objectivo de a testar como método não letal na identificação do sexo de organismos adultos desta espécies. Como principal resultado, verificou‐se a não validade desta característica como potencial método de identificação sexual entre machos e fêmeas de P. lividus. Em conclusão, verificou‐se que os estadios larvares exotróficos de P. lividus, testados como potenciais presas vivas na larvicultura de espécies de crustáceos decápodes marinhos, não apresentam nenhuma vantagem adicional como alimento vivo alternativo ou mesmo complementar face a Artemia spp., no que respeita à obtenção de taxas de sobrevivência superiores ao longo do desenvolvimento larvar. Paralelamente e apesar dos resultados obtidos, este estudo contribui para o aperfeiçoamento, desenvolvimento e aplicação de técnicas e/ou métodos em determinadas áreas da investigação, como é exemplo a ecotoxicologia marinha e estuarina, onde gâmetas e estadios de desenvolvimento embrionário e larvar desta espécie, são utilizados como biomodelos.Fundação para a Ciência e a Tecnologia (FCT, SFRH/BD/36232/2007 e Financiamento Plurianual de Unidades de Investigação e Desenvolvimento (CO/LMG

Ecological risk assessment of sediment management areas : application to Sado Estuary, Portugal

The purpose of this work was to integrate different methodologies to assess the potential ecological risk of estuarine sedimentary management areas, using the Sado Estuary in Portugal as case study. To evaluate the environmental risk of sediment contamination, an integrative and innovative approach was used involving assessment of sediment chemistry, sediment toxicity, benthic community structure, human driving forces and pressures and management areas organic load levels. The basis for decisionmaking for overall assessment was a statistical multivariate analysis appended into a score matrix tables, using a best expert judgment. The integrated approach allowed to identify from the 19 management areas analyzed, three with no risk but other three with high risk to cause adverse effects in the biota, related with the contaminants analyzed. The methodologies used showed to be effective as a support for decision making leading to future estuarine management recommendations.peerreviewe

Evidence for the first multi-species shark nursery area in Atlantic Africa (Boa Vista Island, Cabo Verde)

Funding: This research is part of project NGANDU (The Importance of Shark Populations and Sustainable Ocean Use for Human Well-being in Cabo Verde and São Tomé and Príncipe, West Africa) funded by the Portuguese Foundation for Science and Technology (FCT) and the Aga Khan Development Network (AKDN) under grant agreement FCT AGA-KHAN/541746579/2019. All authors acknowledge funding from FCT under the strategic project UIDB/04292/2020 granted to MARE and project LA/P/0069/2020 granted to the Associate Laboratory ARNET. TM acknowledges funding from the strategic project UIDB/00006/2020 granted to CEAUL. CF acknowledges funding from FCT research contract 2020.03704.CEECIND and FCT grant agreement PTDC/CTA-AMB/30226/2017. VP acknowledges funding from FCT PhD grant 2020.05435.BD. CS acknowledges funding from FCT PhD grant SFRH/BD/117890/2016, FCT research grants under PTDC/CTA-AMB/30226/2017 through FCiencias.ID and AGA-KHAN/541746579/2019 through Nova School of Business and Economics. EN acknowledges funding from FCT PhD grant SFRH/BD/135438/2017. JRP acknowledges funding from FCT research contract 2021.01030.CEECIND. JV acknowledges funding from the Intergovernmental Panel on Climate Change (PhD grant, IPCC Scholarship Programme–Prince Albert II of Monaco Foundation) and the Camões–Instituto da Cooperação e da Língua, I.P. (Scholarship Programme).This study describes the first potential multi-species shark nursery area in Atlantic Africa (Sal Rei Bay – SRB, Boa Vista Island, Cabo Verde). From August 2016 to September 2019, 6162 neonates and juveniles of 5 different shark species were observed in SRB using beach gillnet-based bycatch surveys, namely milk (Rhizoprionodon acutus; n= 4908), scalloped hammerhead (Sphyrna lewini; n= 1035), blacktip (Carcharhinus limbatus; n=115), Atlantic weasel (Paragaleus pectoralis; n= 93) and nurse (Ginglymostoma cirratum; n= 12) sharks. Except for nurse sharks, significant seasonal variations in shark relative abundance were observed, with higher levels being recorded during summer and autumn. These findings, together with local knowledge (interviews to fishermen), denote the consistent use of SRB by juvenile sharks and its preference relative to other areas in the region. Ensuring the protection and conservation of SRB nursery area is especially relevant as, according to IUCN, all identified shark species are threatened with extinction over the near-future – in particular, scalloped hammerheads (critically endangered) and Atlantic weasel sharks (endangered). The effective protection of SRB will not only support the conservation of shark populations, but also of other charismatic fauna (e.g., loggerhead turtles) and broader benthic and pelagic ecosystems.Publisher PDFPeer reviewe

Impacts of deoxygenation and hypoxia on shark embryos anti-predator behavior and oxidative stress

Simple Summary Despite their importance, sharks are among the most endangered ocean species. In addition to overexploitation and the destruction of their natural habitat, climate change is also known to pose a serious threat to them. Among the physico-chemical changes associated with climate change, oxygen loss has been the least studied in terms of its effect on shark physiology and behavior. In this study, we evaluated the impact of deoxygenation (93% air saturation) and hypoxia (26% air saturation) on the anti-predatory behavior and physiology of temperate shark embryos. We found that hypoxia caused a high mortality (44%), significantly increased embryo movement within capsules, and, consequently, reduced the freezing response behavior (a behavior that allows embryos to be unnoticed by predators). Regarding oxidative stress, most biomarkers analyzed were not impacted by the experimental treatments. Overall, our results suggest that the temperate shark's early life stages showed a certain degree of resilience to deoxygenation but not to hypoxia. Climate change is leading to the loss of oxygen content in the oceans and endangering the survival of many marine species. Due to sea surface temperature warming and changing circulation, the ocean has become more stratified and is consequently losing its oxygen content. Oviparous elasmobranchs are particularly vulnerable as they lay their eggs in coastal and shallow areas, where they experience significant oscillations in oxygen levels. Here, we investigated the effects of deoxygenation (93% air saturation) and hypoxia (26% air saturation) during a short-term period (six days) on the anti-predator avoidance behavior and physiology (oxidative stress) of small-spotted catshark (Scyliorhinus canicula) embryos. Their survival rate decreased to 88% and 56% under deoxygenation and hypoxia, respectively. The tail beat rates were significantly enhanced in the embryos under hypoxia compared to those exposed to deoxygenation and control conditions, and the freeze response duration showed a significant opposite trend. Yet, at the physiological level, through the analyses of key biomarkers (SOD, CAT, GPx, and GST activities as well as HSP70, Ubiquitin, and MDA levels), we found no evidence of increased oxidative stress and cell damage under hypoxia. Thus, the present findings show that the projected end-of-the-century deoxygenation levels elicit neglectable biological effects on shark embryos. On the other hand, hypoxia causes a high embryo mortality rate. Additionally, hypoxia makes embryos more vulnerable to predators, because the increased tail beat frequency will enhance the release of chemical and physical cues that can be detected by predators. The shortening of the shark freeze response under hypoxia also makes the embryos more prone to predation.FCT AGA-KHAN/541746579/2019; LISBOA-01-0145-FEDER-028609; DL57/2016/CP1479/CT0023; LA/P/0069/2020; 2021.01030.CEECINDinfo:eu-repo/semantics/publishedVersio

Distinct Bleaching Resilience of Photosynthetic Plastid-Bearing Mollusks Under Thermal Stress and High CO2 Conditions

The impact of temperature on photo-symbiotic relationships has been highly studied in the tropical reef-forming corals but overlooked in less charismatic groups such as solar-powered sacoglossan sea slugs. These organisms display one of the most puzzling symbiotic features observed in the animal kingdom, i.e., their mollusk-plastid association, which enables them to retain photosynthetic active chloroplasts (i.e., kleptoplasts) retrieved from their algae feed sources. Here we analyze the impact of thermal stress (+4°C) and high pCO2 conditions (ΔpH = 0.4) in survival, photophysiology (i.e., bleaching, photosynthetic efficiency, and metabolism) and stress defense mechanisms (i.e., heat shock and antioxidant response) of solar-powered sacoglossan sea slugs, from tropical (Elysia crispata) and temperate (E. viridis) environments. High temperature was the main factor affecting the survival of both species, while pH only affected the survival of the temperate model. The photobiology of E. viridis remained stable under the combined scenario, while photoinhibition was observed for E. crispata under high temperature and high pCO2. In fact, bleaching was observed within all tropical specimens exposed to warming (but not in the temperate ones), which constitutes the first report where the incidence of bleaching in tropical animals hosting photosynthetic symbionts, other than corals, occurs. Yet, the expulsion of kleptoplasts by the tropical sea slug, allied with metabolic depression, constituted a physiological response that did not imply signs of vulnerability (i.e., mortality) in the host itself. Although the temperate species revealed greater heat shock and antioxidant enzyme response to environmental stress, we argue that the tropical (stenotherm) sea slug species may display a greater scope for acclimatization than the temperate (eurytherm) sea slug. E. crispata may exhibit increased capacity for phenotypic plasticity by increasing fitness in a much narrower thermal niche (minimizing maintenance costs), which ultimately may allow to face severe environmental conditions more effectively than its temperate generalist counterpart (E. viridis)

Seahorses under a changing ocean: the impact of warming and acidification on the behaviour and physiology of a poor-swimming bony-armoured fish

Seahorses are currently facing great challenges in the wild, including habitat degradation and overexploitation, and how they will endure additional stress from rapid climate change has yet to be determined. Unlike most fishes, the poor swimming skills of seahorses, along with the ecological and biological constraints of their unique lifestyle, place great weight on their physiological ability to cope with climate changes. In the present study, we evaluate the effects of ocean warming (+4°C) and acidification (ΔpH = −0.5 units) on the physiological and behavioural ecology of adult temperate seahorses, Hippocampus guttulatus. Adult seahorses were found to be relatively well prepared to face future changes in ocean temperature, but not the combined effect of warming and acidification. Seahorse metabolism increased normally with warming, and behavioural and feeding responses were not significantly affected. However, during hypercapnia the seahorses exhibited signs of lethargy (i.e. reduced activity levels) combined with a reduction of feeding and ventilation rates. Nonetheless, metabolic rates were not significantly affected. Future ocean changes, particularly ocean acidification, may further threaten seahorse conservation, turning these charismatic fishes into important flagship species for global climate change issues

Protein analysis and gene expression indicate differential vulnerability of Iberian fish species under a climate change scenario

Current knowledge on the biological responses of freshwater fish under projected scenarios of climate change remains limited. Here, we examine differences in the protein configuration of two endemic Iberian freshwater fish species, Squalius carolitertii and the critically endangered S. torgalensis that inhabit in the Atlantic-type northern and in the Mediterranean-type southwestern regions, respectively. We performed protein structure modeling of fourteen genes linked to protein folding, energy metabolism, circadian rhythms and immune responses. Structural differences in proteins between the two species were found for HSC70, FKBP52, HIF1α and GPB1. For S. torgalensis, besides structural differences, we found higher thermostability for two proteins (HSP90 and GBP1), which can be advantageous in a warmer environment. Additionally, we investigated how these species might respond to projected scenarios of 3° climate change warming, acidification (ΔpH = -0.4), and their combined effects. Significant changes in gene expression were observed in response to all treatments, particularly under the combined warming and acidification. While S. carolitertii presented changes in gene expression for multiple proteins related to folding (hsp90aa1, hsc70, fkbp4 and stip1), only one such gene was altered in S. torgalensis (stip1). However, S. torgalensis showed a greater capacity for energy production under both the acidification and combined scenarios by increasing cs gene expression and maintaining ldha gene expression in muscle. Overall, these findings suggest that S. torgalensis is better prepared to cope with projected climate change. Worryingly, under the simulated scenarios, disturbances to circadian rhythm and immune system genes (cry1aa, per1a and gbp1) raise concerns for the persistence of both species, highlighting the need to consider multi-stressor effects when evaluating climate change impacts upon fish. This work also highlights that assessments of the potential of endangered freshwater species to cope with environmental change are crucial to help decision-makers adopt future conservation strategies.info:eu-repo/semantics/publishedVersio

Impact of ocean acidification in the metabolism and swimming behavior of the dolphinfish (Coryphaena hippurus) early larvae

Since the industrial revolution, [CO2]atm has increased from 280 µatm to levels now exceeding 380 µatm and is expected to rise to 730-1,020 µatm by the end of this century. The consequent changes in the ocean's chemistry (e.g., lower pH and availability of the carbonate ions) are expected to pose particular problems for marine organisms, especially in the more vulnerable early life stages. The aim of this study was to investigate how the future predictions of ocean acidification may compromise the metabolism and swimming capabilities of the recently hatched larvae of the tropical dolphinfish (Coryphaena hippurus). Here, we show that the future environmental hypercapnia (delta pH 0.5; 0.16 % CO2, ~1,600 µatm) significantly (p < 0.05) reduced oxygen consumption rate up to 17 %. Moreover, the swimming duration and orientation frequency also decreased with increasing pCO2 (50 and 62.5 %, respectively). We argue that these hypercapnia-driven metabolic and locomotory challenges may potentially influence recruitment, dispersal success, and the population dynamics of this circumtropical oceanic top predator

Seawater carbonate chemistry and damselfish Pomacentrus amboinensis aerobic physiology

Cleaning symbioses are key mutualistic interactions where cleaners remove ectoparasites and tissues from client fishes. Such interactions elicit beneficial effects on clients' ecophysiology, with cascading effects on fish diversity and abundance. Ocean acidification (OA), resulting from increasing CO2 concentrations, can affect the behavior of cleaner fishes making them less motivated to inspect their clients. This is especially important as gnathiid fish ectoparasites are tolerant to ocean acidification. Here, we investigated how access to cleaning services, performed by the cleaner wrasse Labroides dimidiatus, affect individual client's (damselfish, Pomacentrus amboinensis) aerobic metabolism in response to both experimental parasite infection and OA. Access to cleaning services was modulated using a long-term removal experiment where cleaner wrasses were consistently removed from patch reefs around Lizard Island (Australia) for 17 years or left undisturbed. Only damselfish with access to cleaning stations had a negative metabolic response to parasite infection (maximum metabolic rate—ṀO2Max; and both factorial and absolute aerobic scope). Moreover, after an acclimation period of 10 days to high CO2 (∼1,000 µatm CO2), the fish showed a decrease in factorial aerobic scope, being the lowest in fish without the access to cleaners. We propose that stronger positive selection for parasite tolerance might be present in reef fishes without the access to cleaners, but this might come at a cost, as readiness to deal with parasites can impact their response to other stressors, such as OA