Interactive effects of global warming and eutrophication on a fast-growing Mediterranean seagrass

• Published in: Marine environmental research 2019-03, Vol.145, p.27-38
• Main Authors: Ontoria, Yaiza, Gonzalez-Guedes, Eva, Sanmartí, Neus, Bernardeau-Esteller, Jaime, Ruiz, Juan M., Romero, Javier, Pérez, Marta
• Format: Article
• Language: English
• Subjects: Alismatales; Ammonium; Ammonium compounds; Anoxia; Climate Change; Coastal ecosystems; Cymodocea nodosa; Demographics; Ecosystem; Ecosystems; Enrichment; Environmental changes; Eutrophication; Global Warming; Grasses; Interactive effect; Local planning; Mineral nutrients; Nutrients; Photosynthesis; Sea grasses; Seagrasses; Sediment; Sediments; Signs and symptoms; Survival; Symptoms; Temperature; Temperature effects; Tissue; Water circulation; Water column
• ISSN: 0141-1136; 1879-0291
• DOI: 10.1016/j.marenvres.2019.02.002

Coastal ecosystems, such as seagrasses, are subjected to local (e.g. eutrophication) and global (e.g. warming) stressors. While the separate effects of warming and eutrophication on seagrasses are relatively well known, their joint effects remain largely unstudied. In order to fill this gap, and using Cymodocea nodosa as a model species, we assessed the joint effects of warming (three temperatures, 20 °C, 30 °C and 35 °C) with two potential outcomes of eutrophication: (i) increase in nutrients concentration in the water column (30 and 300 μM), and (ii) organic enrichment in the sediment). Our results confirm that temperature in isolation clearly affects plant performance; while plants exposed to 30 °C performed better than control plants, plants exposed to 35 °C showed clear symptoms of deterioration (e.g. decline of photosynthetic capacity, increase of incidence of necrotic tissue). Plants were unaffected by high ammonium concentrations; however, organic enrichment of sediment had deleterious effects on plant function (photosynthesis, growth, demographic balance). Interestingly, these negative effects were exacerbated by increased temperature. Our findings indicate that in addition to the possibility of the persistence of C. nodosa being directly jeopardized by temperature increase, the joint effects of warming and eutrophication may further curtail its survival. This should be taken into consideration in both predictions of climate change consequences and in local planning. •Temperature increase (up to 30 °C) favors Cymodocea nodosa performances.•Ammonium addition (up to 300 μM) has no negative effects on plants.•C. nodosa is severely altered by organically enriched sediments.•The joint effects of warming and organic C addition may curtail plant survival.