Regional ecosystem variability drives the relative importance of bottom-up and top-down factors for zooplankton size spectra

Abstract

The relative effects of top-down and bottom-up drivers of zooplankton size structure were examined in three limnologically diverse regions of Quebec, Canada. Lake productivity drove biomass of small-sized zooplankton (300-1000 µm) in the Eastern Townships and Laurentian regions, which have high total phosphorus gradients, but was not significant in the low-productivity region, Gouin. Fish species composition was found to affect biomass of large-sized (>1000 µm) zooplankton and was the primary factor affecting zooplankton size structure in the low productivity region. When size structure of the zooplankton communities were described as normalized biomass size spectra, only bottomup factors were significant, as increasing productivity resulted in higher curve peaks and increased parabola curvature. No factors were significantly related to any parameter of the Pareto distribution to describe size spectra. Overall, bottom-up forces were stronger drivers of zooplankton size structure, particularly in regions with wide ranges in lake trophy, while fish predation was more important in regions with low productivity variability.Résumé : Nous avons examiné les effets relatifs des facteurs explicatifs descendants et ascendants de la structure en taille du zooplancton dans trois régions du Québec, Canada, qui diffèrent par les caractéristiques limnologiques de leurs lacs. La productivité lacustre explique la biomasse du zooplancton de petite taille (300-1000 µm) dans les Cantons de l'Est et les Laurentides où il existe de forts gradients de phosphore total; elle n'est cependant pas significative dans la région de Gouin qui possède une faible productivité. La composition spécifique des poissons affecte la biomasse du zooplancton de grande taille (>1000 µm) et elle est le principal facteur à affecter la structure en taille du zooplancton dans la région de faible productivité. Lorsque la structure en taille du zooplancton est présentée sous forme de spectres de taille de la biomasse normalisée, seuls les facteurs ascendants sont significatifs, car une productivité accrue a pour effet de produire des sommets plus élevés dans la courbe et d'augmenter la courbure de la parabole. Aucun des facteurs n'est significativement relié à quelque paramètre que ce soit de la distribution de Pareto qui sert à décrire les spectres de taille. Globalement, les forces ascendantes sont de meilleurs facteurs explicatifs de la structure en taille du zooplancton, particulièrement dans les régions où il existe une forte étendue de trophie dans les lacs, alors que la prédation par les poissons est plus importante dans les régions de faible variation de la productivité.[Traduit par la Rédaction] Finlay et al. 529

A long-term study on crustacean plankton of a shallow tropical lake: the role of invertebrate predation

“…Although in this lake food quantity and quality can be limiting during the cool season (Ferrão-Filho et al, 2003, 2005, there was no indication of a long-term influence on the microcrustaceans. Finlay et al (2007), studying several temperate lakes, concluded that zooplankton were controlled mainly by primary productivity (bottom-up) and not by predators (top-down). However, the seasonal increase in food availability in Lake Monte Alegre, with higher primary productivity of the phytoplankton (1998-99;Feresin et al, 2010Feresin et al, ) or biomass (2011Ferreira, 2013) in the warm season, did not result in corresponding increases of herbivorous microcrustaceans, particularly cladocerans (Fig.…”

“…Furthermore, visual predation is not always determinant in controlling zooplankton, since tactile predation can play the main role (Blumenshine and Hambright, 2003). In some temperate lakes and ponds, the main controlling agent of zooplankton may be primary productivity (Finlay et al, 2007) or temperature and pH (Steiner, 2004), rather than predation. Saunders et al (1999), in their conceptual model of the influence of factors on planktonic herbivores (Fig.…”

On the use of biomass size spectra linear adjustments to design ecosystem indicators

“…Most of these new approaches and recommendations have not had a major impact on how empirical studies have described the size structure in marine and freshwater communities. Nevertheless, the Pareto distribution has been used to describe plankton communities (Quintana et al 2002, Brucet et al 2006, Finlay et al 2007 and to assess the impact of trawling on benthic/demersal communities (Gómez-Canchong et al 2011). A parabolic fit was also used by Finlay et al (2007) when analyzing the factors driving the zooplankton size spectrum in lake communities.…”

GLM-Based Analysis on Seasonal Variation of Fishery Resources in Dapeng Bay, China

“…Biocenosis loses recovery ability and integrity, and the ecosystem stability declines. The proportion of dominant species with small size and low nutrient (r selective species) increases, while the proportion of dominant species with large size and high nutrient (k selective type) decreases [32] [33]. The increasing catching intensity in autumn intensifies degeneration of fishery resources to some extent, resulting in single community structure.…”