RT doctoral thesis
T1 Carbon metabolism and dissolved organic carbon (DOC) fluxes on seagrass communities: insights from plant colonization states, eutrophication and global change related factors
T2 Metabolismo de carbono y flujos de carbono orgánico disuelto (COD) en comunidades de angiospermas marinas: dependencia del estadío de colonización, eutrofización y factores relacionados con el cambio global
A1 Egea Tinoco, Luis Gonzalo
A2 Biología
K1 seagrass
K1 macrophytes
K1 carbon cycle
K1 dissolved organic carbon
K1 global change
AB Coastal vegetated communities are among the most productive ecosystems on Earth.Their role in the global carbon cycle and how they cope with global change may be morerelevant than previously believed. They export large quantities of matter, both inparticulate and dissolved forms to adjacent communities. Dissolved organic carbon (DOC)flux play a central role in the marine carbon cycle as an important driver of primaryproduction for other compartments of the food web. While there has been extensiveresearch on DOC dynamics in the open ocean, the role of coastal ecosystems in the globalDOC cycle is still inadequately understood, even though these habitats tend to accumulatelarge amounts of DOC. Few studies have examined the DOC fluxes by marinemacrophytic communities (macroalgae and seagrasses) under in situ approaches todetermine their overall contribution in the whole system and their subsequent exchangewith adjacent communities. Moreover, coastal vegetated communities, especially thosedominated by seagrasses, are currently considered one of the most threatened ecosystemson Earth because of anthropogenic pressures, including nutrient increase and climatechange. Thus, the overall objective of this Thesis was to evaluate the carbon metabolismand DOC fluxes in communities dominated by seagrasses and elucidate the effects ofhuman–induced disturbances on the carbon dynamics of the community.The results of this Thesis showed that macrophytic communities are highlyautotrophic, with large and variable contributions of their different components of thecommunity, and a DOC source for the plankton community. Increase in nutrientsconcentration triggered that the communites dominated by the macroalge Caulerpaprolifera and the seagrass Cymodocea nodosa moved from autotrophy to heterotrophy incertain seasons of the year and could increase or decrease the DOC release. The responseof seagrass communities when subjected to a pH decrease was complex and showed to bespecies-specific. The pH decrease triggered a significant increase in gross primaryproduction (GPP) and community respiration (R) in seagrasses, which was translated intosucrose increase in aboveground tissues rather than a higher DOC release. Watertemperature was the stressor that had a higher positive effect on carbon metabolism,yielding higher seagrass productivity, growth and DOC release. A direct relationshipbetween productivity increase and larger DOC release was found in communitiesdominated by seagrasses. In addition, a high correlation between DOC release and bothwater temperature and current velocity was found. This Thesis demonstrated that climaticchange and to some extent nutrient enrichment in coastal areas may not be so detrimentalthan previously believed at least for temperate seagrasses, and even may benefit the productivity and resistance of some temperate species (e.g. Cymodocea nodosa) in thefuture.The results of this Thesis underline the high productivity of vegetated coastalecosystems at a local level, which support new insights in the role of the marine primaryproduction in the ocean C sink and the role of the carbon coastal cycle in the global carboncycle. Finally, this Thesis underscores that the role of seagrass meadows in the carboncoastal cycle will be more relevant in the near future, as higher C uptake and DOC releasemay occur under forecasted global change conditions.
YR 2017
FD 2017-09-29
LK http://hdl.handle.net/10498/22832
UL http://hdl.handle.net/10498/22832
LA eng
DS Repositorio Institucional de la Universidad de Cádiz
RD 07-nov-2026