Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, Av. Diagonal 643, 08028, Barcelona, Spain.
Seagrass Ecology Group, Oceanographic Center of Murcia, Spanish Institute of Oceanography, C/ Varadero, 30740, San Pedro del Pinatar, Murcia, Spain.
Mar Environ Res. 2019 Mar;145:27-38. doi: 10.1016/j.marenvres.2019.02.002. Epub 2019 Feb 5.
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.
沿海生态系统，如海草，受到局部（如富营养化）和全球（如变暖）压力源的影响。虽然变暖与富营养化对海草的单独影响相对较为了解，但它们的联合影响在很大程度上仍未得到研究。为了填补这一空白，我们以 C. nodosa 作为模式物种，评估了变暖（三个温度，20°C、30°C 和 35°C）与富营养化的两种潜在结果（i）水柱中营养物质浓度增加（30 和 300 μM），和（ii）沉积物中的有机富集会对海草产生的联合影响。我们的研究结果证实，温度单独作用明显影响植物的表现；尽管暴露在 30°C 下的植物比对照植物表现更好，但暴露在 35°C 下的植物出现了明显的恶化症状（例如，光合作用能力下降，坏死组织的发生率增加）。高浓度的铵对植物没有影响；然而，沉积物的有机富集会对植物的功能（光合作用、生长、人口平衡）产生有害影响。有趣的是，这些负面影响随着温度的升高而加剧。我们的研究结果表明，除了温度升高可能直接危及 C. nodosa 的生存外，变暖与富营养化的联合效应可能进一步限制其生存。在预测气候变化的影响和进行地方规划时，都应考虑到这一点。
