The microplankton succession in the Ría de Vigo revisited: species assemblages and the role of weather-induced, hydrodynamic variability

https://doi.org/10.1016/j.jmarsys.2004.07.009Get rights and content

Abstract

We have analysed meteorological, hydrographic, and microplankton species abundance data, collected every 3–4 days during 1987 in the Ría de Vigo (NW Iberian Peninsula), to investigate the effect of environmental variability on the structure of the microplankton community. Three microplankton assemblages were distinguished, composed chiefly of: small- to medium-sized centric and pennate diatoms (i.e., C- and/or R-species, r-strategists), small-sized organisms from different taxonomic groups (i.e., C- or S-species, r-strategists), and medium- to large-sized dinoflagellates (i.e., S-species, K-strategists). Community changes were related to different scales of meteorological and hydrographic variability. At the seasonal scale, the succession from r-strategists towards K-strategists, or from C- and/or R-species towards S-species, was related with the annual cycle of mixing/stratification and high/low flushing. Within this seasonal pattern, a series of short-term ‘successions’ were identified, the onset of which co-occurred with hydrodynamic changes induced by meteorological disturbances. These results support the conclusions articulated in a previous paper on microplankton community structure during 1991 concerning: (1) the relative persistence of characteristic microplankton assemblages and their ecological interpretation in terms of adaptive strategies, and (2) the key role of weather-induced, hydrodynamic variability, especially at short-term scales, in shaping the structure of the community. The contrasting meteorology in 1987 and 1991 would explain interannual differences of community structure, such as the larger proportion of diatoms in 1991 than in 1987 due to increased intensity and duration of the upwelling seasonal cycle that year. At the species level, the early phase of the seasonal succession was characterised by the coexistence (i.e., single-species biomass, Bi≤40% of total biomass) or alternating dominance (Bi>40% BT) among (C–R) species, while the late part was characterised by the alternating dominance among species with different adaptive strategies. For instance, in September–October, the short-term succession started with the dominance of the (C–R) species Leptocylindrus danicus (∼80% of BT, during 3 weeks), followed by the (S–R) species Ceratium fusus+Ceratium furca (∼70% of BT, 1 week), and finished with the dominance of small microheterotrophs (∼70% of BT, 2 weeks).

Introduction

The species composition of the microplankton community affects key aspects of the functioning of aquatic ecosystems, such as those relative to energetics (e.g., linear or web-like food chains), homeostasis (e.g., low or high diversity), or nutrient cycling (e.g., open or closed mineral cycles) (e.g., Odum, 1969, Reynolds, 1997). However, despite numerous observational (e.g., Karentz and Smayda, 1984), experimental (e.g., Flöder and Sommer, 1999), and modelling studies (e.g., Moloney and Field, 1991), the factors and mechanisms that shape the structure of planktonic communities are still under debate (Reynolds, 1997). Although it is generally accepted that weather-induced, hydrodynamic variability plays a major role (Smayda, 1998) (i.e., allogenic control sensu Reynolds, 1997), it is difficult to demonstrate and quantify its effect on the structure of the microplankton community due to the wide range of temporal scales involved (Kononen, 2001), the complex interplay between factors (Padisák et al., 1993), or the likely lagged response of the organisms to forcing (Duarte, 1990). Besides, it is uncertain and difficult to analyse in natural populations the relevance of self-regulation (i.e., autogenic control sensu Reynolds, 1997), acting through mechanisms such as differential grazing (Cowlishaw, 2000) or allelopathic interactions (Rengefors and Legrand, 2001).

The research conducted by Margalef et al. (1955) and Durán et al. (1956) in the Ría de Vigo established the basic features of succession phenomena in marine phytoplankton communities and the relationship of characteristic phytoplankton assemblages with environmental factors. Form this pioneer research, this enclosed coastal ecosystem has been the focus of numerous investigations dealing with phytoplankton dynamics and its relationship with environmental factors. However, as it happens with similar studies in other marine ecosystems (see, for instance, Cebrián and Valiela, 1999, for the North Atlantic), these investigations either cover long-term periods (≥1 year) at low resolution (i.e., biweekly to monthly sampling) (e.g., Figueiras and Ríos, 1993), or are conducted during brief periods (2–20 days) at high sampling frequency (≥2 samples per week) (e.g., Tilstone et al., 2000) and, thus, disregard, respectively, the effect of short-term variability or the seasonal and long-term scenarios. Recently, Nogueira et al. (2000) analysed high-resolution time series of meteorological, hydrographic, and microplankton species abundance data for the period September 1990–April 1992, showing the relevance of meteorological and hydrographic short-term disturbances on the structural changes of the community. In the present investigation, we followed a similar approach to investigate the dynamics of microplankton community structure in the year 1987, which differed markedly from the previously studied period (centred in the year 1991) in terms of the climatological and meteorological conditions. The analysis involved: (1) the characterisation of the meteorological and hydrographic variability at seasonal and short-term scales; (2) the definition of characteristic microplankton assemblages and their ecological interpretation; and (3) the identification of temporal changes in the structure of the community and its plausible relationship with meteorological and hydrographic variability. The results obtained here were compared with those exposed in Nogueira et al. (2000), offering the opportunity to evaluate the consistency of the conclusions articulated in the aforesaid paper and to assess the significance of interannual variability. We have also considered the succession at the species level, considering the processes of coexistence and dominance.

Section snippets

Materials and methods

The study site, type of time series, and protocols of numerical analysis were, in general terms, similar to those in Nogueira et al. (2000), making the comparison of results straightforward.

Meteorological and hydrographic variability

The meteorological time series were significantly correlated among them (absolute values of the Spearman rank order correlations, ∣rs∣, range between 0.4 and 0.6 (p<0.001), partly due to their strong and coupled seasonality (Fig. 2a and b) (Nogueira et al., 1997). The year 1987 split in two contrasting terms: the ‘winter’ period, from January to mid April and from November to December, characterised by the prevalence of SW winds, high runoff, and low irradiance; and the ‘summer’ period, from

Discussion

We have related the structural changes of the microplankton community with meteorological variability. The significance of allogenic, weather-induced control operating through the modification of the hydrodynamic conditions, mainly in relation to the z- and y-axes in this enclosed coastal ecosystem (i.e., vertical mixing/stratification and washout/dilution following the main axis of the Ría), has been pointed out before (e.g., Figueiras and Pazos, 1991, Figueiras et al., 1995, Figueiras et al.,

Acknowledgements

The authors thank the members of the Grupo de Oceanoloxía of the Instituto de Investigacións Mariñas who collaborated in the sampling, and two anonymous referees whose suggestions considerably improved the manuscript. E. Nogueira acknowledges the receipt of Marie Curie postdoctoral fellowships MAS3-CT97-5049 and MCFI-2000-01958 from the EU. F.G. Figueiras acknowledges the receipt of the EU project HABILE (EVK3-CT-2001-00063).

References (45)

  • M. Durán et al.

    El fitoplancton en la Ría de Vigo de abril de 1954 a junio de 1955

    Invest. Pesq.

    (1956)
  • L. Edler

    Recommendations for marine biological studies in the Baltic Sea. Phytoplankton and chlorophyll

    Balt. Mar. Biol.

    (1979)
  • F.G. Figueiras et al.

    Microplankton assemblages in three Rías Baixas (Vigo, Arosa and Muros, Spain) with a subsurface chlorophyll maximum: their relationships to hydrography

    Mar. Ecol., Prog. Ser.

    (1991)
  • F.G. Figueiras et al.

    Phytoplankton succession, red tides and the hydrographic regime in the Rías Bajas of Galicia

  • F.G. Figueiras et al.

    Red tide assemblage formation in an estuarine upwelling ecosystem: Ría de Vigo

    J. Plankton Res.

    (1994)
  • F.G. Figueiras et al.

    Advection, diffusion and patch development in the Rías Baixas

  • F.G. Figueiras et al.

    Selection of Gymnodinium catenatum under downwelling conditions in the Ría de Vigo

  • S. Flöder et al.

    Diversity in planktonic communities: an experimental test of the intermediate disturbance hypothesis

    Limol. Oceanogr.

    (1999)
  • H.P. Hansen et al.

    Automated chemical analysis

  • G.E. Hutchinson

    The paradox of the plankton

    Am. Nat.

    (1961)
  • F. Ibanez

    Immediate detection of heterogeneities in continuous multivariate, oceanographic recordings. Application to time series analysis of changes in the bay of Villefranche sur Mer

    Limnol. Oceanogr.

    (1981)
  • D. Karentz et al.

    Temperature and seasonal occurrence patterns of 30 dominant phytoplankton species in Narraganset Bay over a 22-year period (1959–1980)

    Mar. Ecol. Progr. Ser.

    (1984)
  • Cited by (28)

    • Assessing the effect of oil spills on the dynamics of the microbial plankton community using a NPZD model

      2022, Estuarine, Coastal and Shelf Science
      Citation Excerpt :

      Values of the model parameters were, when possible, those experimentally determined in the mesocosms whereas the values included in the original model (Annex A) were used for those parameters which were not experimentally determined, provided they were in the range of previous observations. The microbial plankton communities found in the four experiments were representative of the characteristic periods of this coastal upwelling system: spring phytoplankton bloom, summer stratification, autumn upwelling and winter mixing (Figueiras et al., 2002; Nogueira and Figueiras, 2005). Two experiments were carried out during bloom situations: spring and upwelling event.

    • Mussel farming impact on pelagic production and respiration rates in a coastal upwelling embayment (Ría de Vigo, NW Spain)

      2018, Estuarine, Coastal and Shelf Science
      Citation Excerpt :

      During these sampling periods, water column observations were carried out on board R/V ‘Mytilus’ at two stations in the Ría de Vigo (Fig. 1): a reference station (ReS) and a raft station (RaS). The ReS, located in the central channel of the Ría (42 m maximum depth) far from the mussel farming area, has been widely recognized as a reference site for studies regarding short-term and seasonal variability in the Ría de Vigo (e.g. Nogueira et al., 2000; Nogueira and Figueiras, 2005; Crespo et al., 2006). The RaS was situated inside the mussel farming area, within a raft polygon (group of rafts).

    • Tidal and wind-event variability and the distribution of two groups of Pseudo-nitzschia species in an upwelling-influenced Ría

      2014, Deep-Sea Research Part II: Topical Studies in Oceanography
      Citation Excerpt :

      Further, intensive subsurface chlorophyll maxima (SCM) and thin layers dominated by Pseudo-nitzschia spp. have been described off Oregon in the California Current System (McManus et al., 2003; Rines et al., 2002; Trainer et al., 2002). In the Galician Rías, on the northern limit of the Canary Current System (Fig. 1), the annual phytoplankton succession shows a clear temperate-seas seasonal pattern superimposed by the short term (1–2 weeks) and annual variability of the upwelling regime (Margalef et al., 1955; Nogueira and Figueiras, 2005; Nogueira et al., 1997). Toxic harmful algae events in this region occur during the upwelling season and peak in the transition to winter conditions (Escalera et al., 2010; Reguera et al., 2008; Trainer et al., 2010).

    • The growth season of Dinophysis acuminata in an upwelling system embayment: A conceptual model based on in situ measurements

      2014, Deep-Sea Research Part II: Topical Studies in Oceanography
      Citation Excerpt :

      Both in situ division and physically driven accumulation cause blooms at this point. Upwelling-relaxation cycles in the Rías last from days to a few weeks and successive pulses are observed from April to mid-October (Nogueira and Figueiras, 2005; Tilstone et al., 1994, this work). D. acuminata populations will travel oscillating paths in and out of the Rías (Fig. 5B1 and B2).

    View all citing articles on Scopus
    View full text