RT Dissertation/Thesis
T1 Temporal variability of plankton in the north and northwest Iberian shelf : understanding plankton dynamics from monitoring time-series
T2 Variabilidad temporal del plancton en el norte y noreste de la plataforma Ibérica : conociendo la dinámica del plancton a través de series temporales de monitoreo
A1 Buttay, Lucie
K1 3105.10 Dinámica de las Poblaciones
AB The aim of this theses is to explore the pattern of variability of plankton along the northern Atlantic coast of Spain by analyzing the time-series obtained within the RADIALES monitoring program, to investigate the connections between environment and plankton fluctuations and finally, to infer how environment can shape the temporal structure of plankton communities. Because of their short life-span and sensitivity, planktonic organisms constitute an appropriate biological model to study population and community dynamics.The first chapter aim to describe and compare the patterns of variability at 9 stations distributed in 4 across-shelf along the North-western shelf of the Iberian Peninsula. According to the periodicities observed in biomass time-series at all scales, three main spatial domains could be distinguished: oceanic, coastal Cantabrian and coastal Galician. Seasonality accounted for the main proportion of variability in all the stations and a semi-annual component was also observed in the Cantabrian stations. All section presented a positive trend in annually averaged biomass. Average individual weight also varied in the Santander and A Coruña sections suggesting that some change occurred in the zooplankton community structure. Within the second chapter, attention was given to the long-term and seasonal dynamics of zooplankton, in terms of abundance and taxonomic composition, and its relationship with meteo-climatic and hydrographic in the Vigo stations. Total abundance of zooplankton varied annually following on average a unimodal cycle. In the long term, zooplankton abundance exhibited three contrasting periods: A) 1995–2001, of low abundance and low amplitude seasonality, with a stepped increase towards 2001; B) 2001–2006, of high abundance and marked seasonality enclosing the maximum values of the time series; and C) 2006–2010, of intermediate abundance and amplitude of the seasonal cycle. Principal component analysis revealed that all zooplankton taxa increased in abundance from 2001 onward concomitant with sustained trends for upwelling intensity,precipitation and Gulf Stream North Wall position between 2000 and 2005. To explore deeper the processes that have driven the abrupt changes in the Vigo stations, the temporal structure of the zooplankton community has been studied, given rise of the third chapter. Annual oscillation of biomass and abundance increased in 2000 corresponding to the highest amplitudes of Upwelling index and river outflow.. The degree of synchrony appeared to be correlated with the upwelling index and, more closely, with the duration of the upwelling events. The results suggest that amplified seasonality of the environmental variables from 2000 to 2004, combined with a reduction of off-shore exportation by shortening of upwelling events, favored retention in winter, and primary production in summer. Within the fourth chapter we explore the effect of environmental fluctuations, such as nutrient availability, on phytoplankton community temporal structure.From the monthly time-series diatom composition collected at the A Coruña station, we estimated the synchrony among the 12 most abundant species. High synchrony was observed from 1998 to 2002 during a period characterized by the highest amplitude of upwelling index for periodic component of 2 to 3 weeks, 1.5 month and 1.5 year. To better understand the mechanisms and test if changes in the amplitude of nutrient can impact the temporal association between competitors, we employ a simple chemostat model in which two species compete for two fluctuating essential resources. For each possible stochiometric ratio requirement, synchrony increased with the amplitude of nutrient input although the relation is not linear. Indeed, interspecific competition seems to buffer the effect of nutrient fluctuations until a certain threshold where it becomes the main force controlling the temporal association of the species.
YR 2018
FD 2018-10-24
LK http://hdl.handle.net/11093/1066
UL http://hdl.handle.net/11093/1066
LA eng
DS Investigo
RD 15-sep-2024