Nutrient limitation can explain a rapid transition to synchrony in an upwelling-driven diatom community

Identifying the mechanisms controlling the temporal dynamics of ecological communities is key to understand their vulnerability to natural and anthropogenic impacts and to identify early warnings of critical transitions. At community level, inter-specific synchrony is an important indicator of ecosystem stability and variation in function. Using wavelet analysis on time-series of abundance of 12 dominant diatom species, sampled monthly (1994-2009) in a coastal upwelling embayment at the northern limit of the Canary Current Upwelling System, we find a sudden onset of synchrony between 1998 and 2002, concomitant with an increase in the amplitude of the upwelling index at different temporal scales. To better understand the underlying mechanism that could generate this sudden onset of synchrony among competitors, we analyzed a general model of competition between two species for two essential nutrients (e.g., nitrogen and silicate). We incorporate environmental variation by varying the concentration of one of the essential nutrients entering the system. Increase in the amplitude of environmental variation always leads to greater synchrony among competitors. This occurs because the system shifts from a state in which species are limited by different nutrients to one where species are often limited by the same nutrient. We show that the transition from asynchronous to synchronous dynamics can occur suddenly as the amplitude of environmental variation increases. While it is not possible to rule out alternative mechanisms, our model demonstrates that sudden changes in the extent of synchronization should be a common feature when species compete for essential nutrients in variable environments.En prensa3,38

Shift in seasonal amplitude and synchronicity of zooplankton in the northwest Iberian shelf driven by meteo-hydrographic forcing

We have investigated zooplankton temporal dynamics in the northwest Iberian shelf, a temperate ecosystem subject to coastal upwelling-donnwelling processes. To this aim, we have applied wavelet analysis, a methodology able to cope with non-stationary dynamics, to monthly time series of zooplankton abundance and biomass acquired between 1995 and 2011 at two locations over the shelf and to environmental variables known to affect functioning of this ecosystem (wind regime, Ekam transport and river outflows). The seasonal signal of total zooplankton abundance and of the main taxonomic groups showed an abrupt increase in amplitude around 2001 that persisted until the end of the series in 2011. Concurrent with the change in amplitude, there was a synchronization of the seasonal cycle of abundance among taxonomics groups (e.g. copepods, larvaceans, chaetognats...) and copepod species, which persisted for several years although it decreased at the end of the series. Between 2001 and 2004, significant changes in wind regime patterns, linked to variability of the North Atlantic Oscillation, were observed: westerly winds became predominant, river outflow increased and offshore Ekman transport decreased. This meteo-climatic configuration favors retention mechanisms over across-shelf exchage processes due to the reinforcement of the western Iberian buoyant plume (WIBP) and the prevalence of downwelling. We hypothesized that the observed changes in zooplankton dynamics are governed by the amplification of the seasonal signal of these environmental drivers causing enhancement of the retention phenomena

Mesozooplankton dynamics along the Northwest and north Iberian Shelf.

Within the framework of the RADIALES time series monitoring program carried out by the Instituto Español de Oceanografía (IEO), 10 stations were monthly sampled for zooplankton biomass, abundance and taxonomic composition. Additionally, hydrographic features and nutrient concentrations were also measured. From the beginning of the program, a total of 2179 zooplankton samples have been collected. The sampling stations are located along four coastal-ocean sections in the Northwest and North Iberian shelf, off Vigo, A Coruña, Gijón and Santander beginning in 1994, 1991, 2001, 1992, respectively. There is classically a contrasted situation between the Galician and the Cantabrian coast. Since the Galician coast represents the northern limit of the Canary upwelling system, coastal upwelling has a major influence on their hydrodynamic behavior and nutrient distributions. In the Cantabrian coast, upwelling is restricted to occasional events during summer and nutrient fertilization depends mostly on the deep convection occurring during winter. In this communication we aim to describe the long-term dynamics of zooplankton biomass for oceanic and shelf waters of the northwest and north Iberian Peninsula focusing in the common period sampled in all the stations (2001-2013, representing 1405 sampling events). We used a method able to cope with the non-stationary nature of the data, namely wavelet analysis. It allows describing the periodic components of the signal as classically obtained with the Fourier analysis. But in addition, the wavelet analysis approach provides information of the variability of the periodic components along the time series. Indeed the principal periodic components (1, 1,5 and 3 years) appear to be transient in both hydrologic and zooplankton biomass series. A pair-wise comparison between the power spectrum matrices of each zooplankton biomass time series allowed us to detect common dynamics between the coastal Cantabrian stations, the oceanic Cantabrian stations and the Galician ones

Mare Incognitum: A Glimpse into Future Plankton Diversity and Ecology Research

With global climate change altering marine ecosystems, research on plankton ecology is likely to navigate uncharted seas. Yet, a staggering wealth of new plankton observations, integrated with recent advances in marine ecosystem modeling, may shed light on marine ecosystem structure and functioning. A EuroMarine foresight workshop on the “Impact of climate change on the distribution of plankton functional and phylogenetic diversity” (PlankDiv) identified five grand challenges for future plankton diversity and macroecology research: (1) What can we learn about plankton communities from the new wealth of high-throughput “omics” data? (2) What is the link between plankton diversity and ecosystem function? (3) How can species distribution models be adapted to represent plankton biogeography? (4) How will plankton biogeography be altered due to anthropogenic climate change? and (5) Can a new unifying theory of macroecology be developed based on plankton ecology studies? In this review, we discuss potential future avenues to address these questions, and challenges that need to be tackled along the way