Nutrient enrichment affects the seagrass Cymodocea serrulata and induces changes to its epiphytic cyanobacterial community
(English)Manuscript (preprint) (Other academic)
To better understand how elevated water column nutrient levels affect the performance of the seagrass Cymodocea serrulata as well as the composition and density of its associated epiphytes, two sets of experiments were carried out where nutrient concentration were manipulated in a flow though system containing seagrasses. The photosynthetic performance, growth characteristics and nutrient content (N:P) were followed for C. serrulata. Simultaneously the biomass, species composition for the epiphytic cyanobacteria, in particular diazotrophs was monitored. The photosynthetic capacity of seagrasses decreased with increase in nutrient concentrations and exposure time. Nutrient contents of seagrass leaves and epiphytes decreased after nutrient addition. A higher diversity of both heterocystous and non-heterocystous cyanobacteria was observed in the experimental seagrasses as compared with natural field samples. Many of the cyanobacterial sequences retrieved represented uncultured and potentially novel diazotrophic phylotypes. Diel nitrogenase activity measurements verified the presence of a distinct proportion of diazotrophs, which was negatively affected by moderate nutrient levels. These results demonstrate that seagrasses were physiologically stressed by the increased nutrient level as revealed by low maximum quantum yields, although the effect was not instant. In contrast the epiphytes whose response was apparent during the short term exposure to moderate nutrient concentration which also promoted rapid change in their composition.
Cymodocea serrulata, diazotrophy, epiphyte, cyanobacteria, nutrient enrichment; photosynthesis, seagrasses
Research subject Plant Physiology
IdentifiersURN: urn:nbn:se:su:diva-55868OAI: oai:DiVA.org:su-55868DiVA: diva2:408781