Abstract collection session 6: Coral reefs and their response to anthropogenic disturbances in the past, present, and future


Novel anti-biofouling coatings and their potential to enhance coral restoration practices

by Lisa Röpke, David Brefeld, Andrew Negri, Ulrich Soltmann and Andreas Kunzmann

Leibniz Centre forTropical Marine Research GmbH (ZMT) | University of Bremen | Australian Institute of Marine Science |Gesellschaft zur Förderung von Medizin-, Bio- und Umwelttechnologien e. V. (GMBU) | Leibniz Centre for Tropical Marine Research GmbH (ZMT)

Tropical coral reefs are suffering from many human induced stressors worldwide. Carbon emission induced water temperature rise, ocean acidification, nutrient and waste water discharges, sedimentation, habitat loss due to construction works and overfishing are only a few to mention. Scientists are developing and exploring new methods to assist corals in order to withstand and overcome these threats by applied interdisciplinary sciences. The bottleneck and most fragile part in the puzzle of coral reef survival is reproduction. Corals will only sustain, if their potential to grow is maximized. Corals and their offspring suffer from increased algae overgrowth, facilitated by nutrient inputs and overfishing. An increased reduction of herbivorous species, as well as nutrient discharges will ultimately result in major algae dominated habitats and the last coral reefs and their small sized offspring will be overgrown and lost.

Therefore, innovative and environmentally benign anti-biofouling coatings, aiming to inhibit algae growth and create a favorable environment for coral offspring, were tested. The effects of three novel anti-biofouling coatings on the fouling community, survival and growth of coral settlers were assessed to explore the potential application of the coatings as a new tool for coral reef restoration practices.


Physiological and proteomic impacts of warming and acidification on different photosymbiotic calcifiers show distinctive links to symbiont condition and pH-regulation

by Marleen Stuhr, Louise P Cameron, Bernhard Blank-Landeshammer, Laxmikanth Kollipara, Claire EReymond, Albert Sickmann, Hildegard Westphal and Justin Ries

Interuniversity Institute for MarineSciences, Eilat | Department of Marine and Environmental Sciences, Marine Science Center,Northeastern University, Boston | Leibniz Institut für Analytische Wissenschaften – ISAS – e.V., Dortmund| Leibniz Institut für Analytische Wissenschaften – ISAS – e.V., Dortmund | Leibniz Centre for TropicalMarine Research (ZMT), Bremen | Leibniz Institut für Analytische Wissenschaften – ISAS – e.V.,Dortmund | Leibniz Centre for Tropical Marine Research (ZMT), Bremen | Department of Marine andEnvironmental Sciences, Marine Science Center, Northeastern University, Boston

Globally important calcifiers such as corals and large benthic foraminifera exhibit complex responses to environmental stressors associated with anthropogenic CO2. While high seawater pH supports calcification, elevated pCO2 may promote photosynthesis by algal symbionts. Proteomic regulations may facilitate acclimatization to global impacts as proteins are typically the effectors of biological function. To investigate the mechanisms underlying their responses to global change, three tropical coral species and one common reef-foraminifera were exposed to a range of combined ocean acidification and warming scenarios for two months. Physiological parameters and differential protein abundances, quantified via label-free LC-MS/MS-based proteomics, from selected treatments were explored alongside pH-microsensor analyses. All corals increased calcification rates and photosymbiont abundance under elevated pCO2, except under warming scenarios in which they showed photosymbiont loss and reduced calcification rates. Species-specific effects of ocean acidification were reflected in the proteomic responses, however, we found common increases of proteins involved in antioxidant synthesis, calcium-binding messenger proteins and energy production enzymes, but reductions of ribosomal constituents and proteins involved in cell development. In comparison, foraminifera and their photosymbionts were hardly affected by elevated pCO2, whereas elevated temperature reduced growth. Exposure to combined stressors reduced pore sizes along with increased microenvironmental pH-upregulation. Stable physiological performance at moderate pCOwas rendered by substantial proteomic variations in host and symbionts, while minimal proteomic response to higher pCO2 levels may represent impairment of acclimatization mechanisms. Hence, while linkages between photosymbiont abundance, regulation of calcifying fluid pH, and calcification were identified in corals, reef-foraminifera maintained photosymbiont levels despite altered ion exchange rates, putatively related to micro-skeletal adjustments. Overall, our experiment suggests that photosymbiotic calcifiers can cope with ocean acidification through intensification of photosynthesis and other metabolic pathways, unless thermal stress induces photosymbiont loss. It further indicates trade-offs towards particular cellular functions and highlights species-specific key proteins shaping physiological plasticity.


Microplastic particle incorporation and identification in scleractinian coral skeleton

by Florian Hierl, Henry C. Wu and Hildegard Westphal

Leibniz Centre for Tropical Marine Research |Leibniz Centre for Tropical Marine Research | Leibniz Centre for Tropical Marine Research

Anthropogenic litter pollution of the marine environment is an emerging threat and is being more and more recognized by society. With an increasing production volume of litter, the amount of plastics entering the marine environment increases each year as well. Initially floating plastic particles are subject to degradation and biofouling, ultimately reaching marine benthos and massively impacting marine health. These microplastics (<5 mm) originate from either degradation of larger plastic pieces or industrial production and have been detected everywhere in the ocean from the surface to the deep-sea and on beaches and coastal habitats. Several laboratory studies have proven, that due to their shape, texture and taste, microplastics can be mistaken for food items by marine organisms. Although only little is known about the ultimate effects of microplastic pollution in coral reefs, its impacts need to be understood urgently. In this study, we aim to determine the interactions between microplastics (polyethylene terephthalate (PET)) and coral skeletal production. We conducted a 5-month aquarium-based experiment exposing four different coral species of various polyp sizes and coral surface morphologies to high concentrations of PET. We observed notably increased mucus production by the corals during times of PET exposure, which can be seen as a defence mechanism against pollutant induced stress. Our skeleton analyses revealed significant alterations to its natural growth form by utilising high-resolution micro-computed tomography and the production of petrographic thin sections for Scanning Electron Microscopy, and Energy Dispersive X-ray Spectroscopy (EDX). While numerous PET particles were observed to be ingested and later expelled by the corals, some PET particles and fibres of unknown origin were integrated into the skeleton during the process of calcification. This integration into skeletal material is potentially caused by tissue necrosis and subsequent overgrowth following adhesion or the ingestion of plastic particles.


Adaptability of deepwater corals Caryophyllia (Caryophyllia) smithii to changing ocean pH

by Lukas Bublies, Henry C. Wu, Anette Meixner, Julia Michaelis, Edwige Pons-Branchu, SimoneKasemann, Claire Reymond and Hildegard Westphal

Universität Bremen FB5 Geowissenschaften M.Sc.Marine Geosciences | ZMT | Marum | ZMT | LSCE | Marum | ZMT | ZMT

Caryophyllia (Caryophyllia) smithii is a slow-growing aragonitic species of scleractinian coral that occurs in cold to temperate waters from 50 to 1000 m depth. Specimens of C. smithii been sampled during the Meteor M129 Cruise off the coast of Senegal and Mauretania. The samples have been analyzed for trace elements, as well as boron isotopic ratios (δ11B), as a whole resulting in average element values for the entire lifespan of the coral. Using trace element ratios we were able to reconstruct average water temperature and primary productivity during the lifespan of the corals. The relatively high δ11B composition of all specimens ranges from 24.58 ‰ to 26.16 ‰. These values lie above the pH-dependent seawater borate equilibrium curve. This is an indicator for strong up-regulation of the pH of the calcifying fluid (pHcf) inside the coral relative to seawater. Compared to previous measurements of C. smithii in the Mediterranean Sea the δ11B are significantly lower (Δ = 2‑4 ‰), resulting in much lower pHcf by about 0.4 pH units. Upregulation in the pHcf seems to be dependent on location and the surrounding seawater and is not locked to an optimal pH. A major aspect of the current climate change is ocean acidification. This makes it harder for calcifying organisms to secrete their shell from seawater. Therefore it is vital to understand the mechanisms behind pH regulation in corals, to estimate the threat that rising atmospheric CO2 and therefore lower ocean pH has on deep-water corals.



Poster

Behavioral responses of coral larvae to novel anti-biofouling coatings
by Lisa Röpke, David Brefeld,  Andrew Negri, Ulrich Soltmann and Andreas Kunzmann

Leibniz Centre for Tropical Marine Research | Universität Bremen | Australian Institute of Marine Science | Gesellschaft zurFörderung von Medizin-, Bio- und Umwelttechnologien e. V. | Leibniz Centre for Tropical MarineResearch

Coral reefs are under threat by local and global anthropogenic stressors. These stressors often lead to a decline in coral cover and ultimately, the loss of valuable ecosystem services. Mitigation of these stressors in combination with active coral reef rehabilitation programs could help to secure the survival of reef ecosystems and their affiliated ecosystem services for future generations.

The sexual proliferation of corals has a high potential to provide a large number of genetically diverse coral recruits for coral reef restoration projects. However, the number of adult corals that can be propagated this way is limited, due to the high mortality of coral larvae and recruits. The survival of juvenile corals could potentially be improved by inhibiting the growth of the surrounding biofouling community that competes with them for light and space.

Anti-biofouling coatings are commonly used to reduce the degree of undesired biofouling on submerged hard surfaces and could potentially be used to alleviate this competition.

Here, the effects of three novel anti-biofouling coatings on the motility and settlement of coral larvae were assessed to explore the potential of the coatings as a new tool for coral reef restoration practices.