Cold-water corals and anthropogenic stressors – effects of sediment load on respiration, growth and behaviour of juvenile Caryophyllia huinayensis

Juergen.Laudien [ at ]


The steep walls of Chilean fjords are biodiversity hotspots and characterized by high precipitation rates, high river run-off and natural landslides with an inherent high sediment input. These sedimentation rates are likely to increase in the future due to expanding salmonid farming and coastal road construction. Caryophyllia huinayensis, is a Scleractinia, solitary cold-water coral (CWC) growing on steep slopes and overhanging portions of the fjord walls, which may indicate a sensitivity to sedimentation. However, actual data on the susceptibility to sediment of this CWC species is lacking. Furthermore, there is a deficit of information on juvenile CWC dealing with sedimentation stress, which is why this is the first study on this topic. The aim of this work was to investigate whether increased sediment concentrations affect the overall performance of juvenile specimens of C. huinayesis, measuring over three-months the coral growth, behaviour and respiration rates. The study consists of an ex-situ experiment which included three different treatments: i) the control treatment: with the current natural sediment concentration of Comau Fjord, ii) a 100-fold sediment concentration and iii) a 1000-fold sediment concentration than the control. The most remarkable result demonstrates that corals under the highest sediment concentrations display a significant decreased polyp activity (60 % lower) hence affecting pray capture thus nutrition, leading to a significant reduced growth rate (natural 0.14 ± 0.09 mg d-1; 100-fold: 0.09 ± 0.07 mg d-1; 1000-fold concentration: 0.003 ± 0.009 mg d-1). Furthermore, polyps partly retracted their tissue with increasing sediment load. The results show that all these effects seem to be lower for corals facing vertical downwards than for individuum’s growing horizontally. Another important result reveals that long-time exposed (13 weeks) juveniles significantly decrease their oxygen consumption which is directly related to increasing sediment load. Whereas newly exposed individuals (24 h) showed no significant change in their respiration rate under the influence of increased sedimentation load. The results of this experiment contribute to a better understanding of the abilities of CWC recruits to cope with anthropogenic impacts. This information is fundamental as the viability of the juveniles is indispensable for future coral populations and the so called ‘Cold-Water Stony Coral Forests‘. Consequently, management plans for the fjord need to consider the harmful effects of increased sedimentation on threatened CWC’s.

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Thesis (Master)
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Helmholtz Cross Cutting Activity (2021-2027)
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Fähse, M. (2021): Cold-water corals and anthropogenic stressors – effects of sediment load on respiration, growth and behaviour of juvenile Caryophyllia huinayensis , Master thesis, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung und Carl von Ossietzky Universität Oldenburg.

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