Species-Specific Response of Corals to Imbalanced Ratios of Inorganic Nutrients

Abstract

Dissolved inorganic phosphorus (DIP) is a limiting nutrient in the physiology of scleractinian corals. Anthropogenic addition of dissolved inorganic nitrogen (DIN) to coastal reefs increases the seawater DIN:DIP ratio and further increases P limitation, which is detrimental to coral health. The effects of imbalanced DIN:DIP ratios on coral physiology require further investigation in coral species other than the most studied branching corals. Here we investigated the nutrient uptake rates, elemental tissue composition and physiology of a foliose stony coral, Turbinaria reniformis, and a soft coral, Sarcophyton glaucum, exposed to four different DIN: DIP ratios (0.5:0.2, 0.5:1, 3:0.2, 3:1). The results show that T. reniformis had high uptake rates of DIN and DIP, proportional to the seawater nutrient concentrations. DIN enrichment alone led to an increase in tissue N content, shifting the tissue N:P ratio towards P limitation. However, S. glaucum had 5 times lower uptake rates and only took up DIN when the seawater was simultaneously enriched with DIP. This double uptake of N and P did not alter tissue stoichiometry. This study allows us to better understand the susceptibility of corals to changes in the DIN:DIP ratio and predict how coral species will respond under eutrophic conditions in the reef.

Diversity of lipid profiles of Symbiodiniaceae under temperature and nutrient stress

“…Therefore, species specific symbiont lipid composition and adaptability may also play a key role in coral energetics and resilience to environmental change (Sampayo et al, 2008;Boulotte et al, 2016). For example, nutrient limitation, alterations to the N:P ratio, and temperature extremes are known to disrupt the stability of some coral-Symbiodiniaceae symbioses, ultimately increasing susceptibility to coral bleaching and mortality (Ezzat et al, 2016;Rosset et al, 2017;Blanckaert et al, 2023). As nutrient concentrations and temperature can affect microalgae lipid composition (Holm et al, 2022;Gao et al, 2023), the plasticity of Symbiodiniaceae lipid composition, and thus what is translocated to the coral hosts, could determine the susceptibility of coral-Symbiodiniaceae associations to climate change and potential for the poleward range shifts of corals (Nielsen and Petrou, 2023).…”