Catriona Clemmesen

Eutrophication-driven harmful algal blooms (HABs) can have secondary effects on larval fishes that rely on estuaries as nurseries. However, few studies worldwide have quantified these effects despite the global rise in eutrophication. This study presents a novel approach using biochemical body condition analyses to evaluate the impact of HABs on the growth and body condition of the larvae of an estuarine resident fish. Recurrent phytoplankton blooms of Heterosigma akashiwo occur in the warm-temperate Sundays Estuary on the southeast coast of South Africa. The response in body condition and assemblage structure on larval estuarine roundherring (Gilchristella aestuaria) was measured in conjunction with bloom conditions, water quality and zooplanktonic prey and predators. Larvae and early juveniles were sampled during varying intensity levels, duration and frequency of hypereutrophic blooms. This study demonstrated that extensive HABs could significantly impact larval roundherring, G. ...

Cape anchovy Engraulis encrasicolus is an ecologically and economically important pelagic fish species occurring along the coast of South Africa. A recent eastward shift in Cape anchovy distribution indicates that environmental conditions are becoming more favorable for the species on the east coast. This shift is particularly important in the sheltered Algoa Bay region, a nursery area for fish larvae. However, the relatively low productivity of the Agulhas Current Large Marine Ecosystem on the eastern coast of South Africa may result in an anchovy population in poorer nutritional condition and with slower growth rates than the west coast population. Using otolith and nucleic acid analyses, the growth rates of anchovy larvae from the western and southeastern coasts of South Africa were compared. The otolith analysis results indicated that, at any given age, individual growth rates for anchovy larvae were higher on the southeast coast than on the west coast. The RNA:DNA values also i...

The reliable production of marine fish larvae is one of the major bottlenecks in aquaculture due to high mortalities mainly caused by infectious diseases. To evaluate if the compound poly-ß-hydroxybutyrate (PHB) might be a suitable immunoprophylactic measure in fish larviculture, its capacity to improve immunity and performance in European sea bass (Dicentrarchus labrax) yolk-sac larvae was explored. Dietary PHB was applied from mouth opening onwards to stimulate the developing larval immune system at the earliest possible point in time. Larval survival, growth, microbiota composition, gene expression profiles and disease resistance were assessed. PHB administration improved larval survival and, furthermore, altered the larva-associated microbiota composition. The bacterial challenge test using pathogenic Vibrio anguillarum revealed that the larval disease resistance was not influenced by PHB. The expression profiles of 26 genes involved e.g. in the immune response showed that PHB affected the expression of the antimicrobial peptides ferritin (fer) and dicentracin (dic), however, the response to PHB was inconsistent and weaker than previously demonstrated for sea bass post-larvae. Hence, the present study highlights the need for more research focusing on the immunostimulation of different early developmental stages for gaining a more comprehensive picture and advancing a sustainable production of high quality fry.

Due to atmospheric accumulation of anthropogenic CO2 the partial pressure of carbon dioxide (pCO2) in surface seawater increases and the pH decreases. This process known as ocean acidification might have severe effects on marine organisms and ecosystems. The present study addresses the effect of ocean acidification on early developmental stages, the most sensitive stages in life history, of the Atlantic herring (Clupea harengus L.). Eggs of the Atlantic herring were fertilized and incubated in artificially acidified seawater (pCO2 1260, 1859, 2626, 2903, 4635 µatm) and a control treatment (pCO2 480 µatm) until the main hatch of herring larvae occurred. The development of the embryos was monitored daily and newly hatched larvae were sampled to analyze their morphometrics, and their condition by measuring the RNA/DNA ratios. Elevated pCO2 neither affected the embryogenesis nor the hatch rate. Furthermore the results showed no linear relationship betweenpCO2 and total length, dry weight, yolk sac area and otolith area of the newly hatched larvae. For pCO2 and RNA/DNA ratio, however, a significant negative linear relationship was found. The RNA concentration at hatching was reduced at higher pCO2 levels, which could lead to a decreased protein biosynthesis. The results indicate that an increased pCO2 can affect the metabolism of herring embryos negatively. Accordingly, further somatic growth of the larvae could be reduced. This can have consequences for the larval fish, since smaller and slow growing individuals have a lower survival potential due to lower feeding success and increased predation mortality. The regulatory mechanisms necessary to compensate for effects of hypercapnia could therefore lead to lower larval survival. Since the recruitment of fish seems to be determined during the early life stages, future research on the factors influencing these stages are of great importance in fisheries science.

Frommel, Andrea, Maneja, Rommel, Lowe, D., Geffen, A., Folkvord, A., Piatkowski, Uwe and Clemmesen, Catriona (2011) Harmful effects of ocean acidification in a commercially important fish larvae: Atlantic Cod [Poster] In: EPOCA Third Annual Meeting, Royal ...

Frommel, Andrea, Maneja, Rommel, Geffen, Audrey, Folkvord, Arild, Lowe, D., Havenhand, J., Piatkowski, Uwe and Clemmesen, Catriona (2010) Effects of ocean acidification on the growth and development in North Sea cod (Gadus morhua)[Talk] In: Joint EPOCA, ...

TheGreifswalder Bodden (GWB) is considered to be themost important spawning and nursery area for thewestern Baltic spring-spawning herring.However, the biotic and abiotic reasons for this are still unclear. Consequently, we investigated larval growth conditions in theGWB and in the Kiel Canal (KC), another nursery and spawning area of Baltic herring.We investigated prey quantity and quality [copepod abun-dance and essential fatty acid (EFA) concentration] as well as biochemically derived growth rates and fatty acid content of larval herring in spring 2011. A significant correlation between larval growth and larval EFA concentration could be observed in the GWB. The highest growth rates and EFA concentrations in the larval herring coincided with high food quality. Compensating effects of food quality on food quantity and vice versa could be observed in both the GWB and the KC. While larval growth rates in the KC were high early in the season, highest growth rates in the GWB were achi...

Common garden experiments were conducted to test whether a broad physiological plasticity and acclimation account for the significant greater salinity tolerance of Temora longicornis of mesohaline origin compared to populations from polyhaline regions of the Baltic Sea. Using full sib clutches from the Kattegat and the Bornholm Sea split across a salinity gradient of 8-20 offspring survival revealed that the tolerance of low salinity results from genotype variation and local adaptation as a result of selection rather than a physiological euryhalinity of the species. This adaptation has relevant implication for the understanding of the environmental control of the species’ dynamics. Progress: All experimental work is completed. Data analysis and manuscript preparation is in progress. A detailed report of current status is attached as Appendix 1. Deviations: No deviations from the work plan. Introduction: Despite being largely mesohaline, the open basins of the Baltic Sea are dominate...

Our oceans are changing as high levels of atmospheric CO2 dissolve into seawater and lower its pH to become more acidic. The average pH of the world’s oceans has dropped from an estimated 8.2 to around 8.1 since the beginning of industrialisation. It has been predicted that it will fall by another 0.4 units by 2100. While it is already known that ocean acidification will have damaging effects on some marine creatures, its impacts vary by species and very little work has been done on herring.

The reliable production of marine fish larvae is one of the major bottlenecks in aquaculture due to high mortalities mainly caused by infectious diseases. To evaluate if the compound poly-β-hydroxybutyrate (PHB) might be a suitable immunoprophylactic measure in fish larviculture, its capacity to improve immunity and performance in European sea bass (Dicentrarchus labrax) yolk-sac larvae was explored. PHB was applied from mouth opening onwards to stimulate the developing larval immune system at the earliest possible point in time. Larval survival, growth, microbiota composition, gene expression profiles and disease resistance were assessed. PHB administration improved larval survival and, furthermore, altered the larva-associated microbiota composition. The bacterial challenge test using pathogenic Vibrio anguillarum revealed that the larval disease resistance was not influenced by PHB. The expression profiles of 26 genes involved e.g. in the immune response showed that PHB affected ...

Productivity of marine fish stocks is known to be affected by environmental and ecological drivers, and global climate change is anticipated to alter recruitment success of many stocks. While the direct effects of environmental drivers on fish early life stage survival can be quantified experimentally, indirect effects in marine ecosystems and the role of adaptation are still highly uncertain. We developed an integrative model for the effects of ocean warming and acidification on the early life stages of Atlantic cod in the Barents Sea, termed SCREI (Simulator of Cod Recruitment under Environmental Influences). Experimental results on temperature and CO2 effects on egg fertilization, egg and larval survival and development times are incorporated. Calibration using empirical time series of egg production, temperature, food and predator abundance reproduces age-0 recruitment over three decades. We project trajectories of recruitment success under different scenarios and quantify confi...

How fisheries will be impacted by climate change is far from understood. While some fish populations may be able to escape global warming via range shifts, they cannot escape ocean acidification (OA), an inevitable consequence of the dissolution of anthropogenic carbon dioxide (CO2) emissions in marine waters. How ocean acidification affects population dynamics of commercially important fish species is critical for adapting management practices of exploited fish populations. Ocean acidification has been shown to impair fish larvae's sensory abilities, affect the morphology of otoliths, cause tissue damage and cause behavioural changes. Here, we obtain first experimental mortality estimates for Atlantic cod larvae under OA and incorporate these effects into recruitment models. End-of-century levels of ocean acidification (~1100 μatm according to the IPCC RCP 8.5) resulted in a doubling of daily mortality rates compared to present-day CO2 concentrations during the first 25 days po...

Clemmesen, Catriona, Frommel, Andrea, Maneja, Rommel, Geffen, A., Folkvord, A., Lowe, D., Malzahn, Arne and Piatkowski, Uwe (2011) Ocean Acidification effects on commercially important fish species [Talk] In: 2. Annual Meeting of BIOACID, 26.-30.09. 2011, Bremen, ...

A laboratory calibration study was undertaken with juvenile Sepia officinalis (80–85 g initial wet weight) to investigate the effects of different food rations and different starving intervals on RNA/dry weight (DW) ratios and RNA/DNA ratios in cephalopod mantle muscle at two different temperatures. The digestive gland index was also used as an additional indicator of recent growth. High food rations

Frommel, Andrea, Maneja, Rommel, Geffen, A., Folkvord, A., Lowe, D., Malzahn, Arne, Piatkowski, Uwe and Clemmesen, Catriona (2011) Ocean Acidification: A Problem for Fish?[Talk] In: 2011 ASLO Aquatic Sciences Meeting, 13.02.-18.02. 2011, San Juan, ...

ABSTRACT This study investigated the effect of ocean acidification (OA) and warming on the survival of Western Baltic cod (Gadus morhua) larvae reared in the laboratory in 90 L tanks at ambient CO2 concentrations (400 ppm) and CO2 concentrations as predicted for the end of the century (1000 ppm). Temperature (7°C and 9°C) as an additional stressor was studied in a full-factorial design with CO2. Larvae were fed natural plankton at a low food density and mortality was measured daily by removing dead larvae from the tanks. Growth measurements including standard length, myotome height as well as otolith measurements were analysed. The results clearly show that an increased CO2 concentration had a significant negative effect on the survival of the larvae mostly during critical phases in larval development. An increase in temperature, however, did not further increase mortality. Growth and otolith measurements strongly suggest an increase in growth rate and size-selective mortality with selection for larger larvae occurring under increased CO2 conditions. The results will be compared and discussed in relation to other experimental results with respect to OA and cod larvae. The larval response to OA seems to be dependent on the developmental stage and their nutritional condition.