Interactive effects of omnivorous fish and nutrient loading on net productivity regulation of phytoplankton and periphyton

Abstract

Top predators and nutrient loading are key components in the regulation of community structure and biomass in aquatic ecosystems. However, few studies have addressed how these 2 components interact to determine metabolic variables of the community, such as oxygen production and respiration rates. The pelagic zone has been the focus of most research on trophic cascades. Nevertheless, recent data increasingly show the importance of periphyton to the functioning of lakes. We conducted a fully factorial field experiment in enclosures within a humic coastal lagoon to analyze the interacting effects of nutrient addition (N and P) and the presence/absence of omnivorous fish on phytoplankton and periphyton net primary productivity. Fish presence positively affected net planktonic productivity, especially when nutrients were added. However, fish presence negatively affected net periphytic productivity, probably due to 2 non-exclusive mechanisms: the increase in competition with phytoplankton, which was released from zooplankton grazing, and the direct periphytic biomass consumption by fish. We conclude that fish can alter fundamental ecosystem processes in lakes, such as internal carbon dynamics, by increasing the relative importance of pelagic to periphyton productivity. KEY WORDS: Trophic cascade · Aquatic metabolism · Cross-habitat linkage · Food web · Shallow lakeResale or republication not permitted without written consent of the publisher

Synergistic control of CO2 emissions by fish and nutrients in a humic tropical lake

“…This species is typically omnivorous, and an extensive stomach content analysis of resident fish captured in Lake Cabiúnas revealed a diet consisting of both primary producers, such as algae (mainly from classes Bacillariophyceae and Zygnemophyceae) or cyanobacteria, and herbivores, such as zooplankton (mainly phylum Rotifera and classes Branchiopoda, Maxillopoda, and Ostracoda) or snail larvae (Coutinho et al 2000). Yellow tetra in Lake Cabiúnas may also feed selectively on periphyton depending on the phytoplankton community (Guariento et al 2010). Fish were captured and kept for 24 h in a cage submerged in the lake, following which they were added to the mesocosms (?Fish and ?Nutr?Fish conditions, respectively) at densities often observed in situ [13 individuals (ind.)…”

“…Yellow tetra (Hyphessobrycon bifasciatus; family Characidae) is a widely distributed fish species in inland waters in Brazil and is abundant in the lake that is the focus of the study reported here (Coutinho et al 2000). The potential effects of yellow tetra on the CO 2 balance in aquatic ecosystems are difficult to predict, since this species feeds on both herbivores (zooplankton) and primary producers (algae) in the food web (Coutinho et al 2000;Guariento et al 2010).…”

The role of abiotic and biotic environmental factors in shaping epiphyton on common reed in shallow, hydrologically transformed, temperate lakes

“…example, to Fragilariaceae may be expected, as their abundance correlated negatively with fish abundance. The direct periphytic biomass consumption by omnivorous fish was showed in experimental study by Guariento et al (2010). Blanco et al (2008) showed that zooplanktivorous fish enhanced the abundance of Euglenophyceae and Zygnematophyceae, as well as algal species richness and diversity, by secreting biogenic substances.…”

“…Grazing pressure may be very important biotic factor shaping epiphyton assemblages (Abe et al, 2007;Guariento et al, 2010;Tarkowska-Kukuryk, 2013). In the studied lakes, the pressure from fish grazing (with S. erythrophthalmus as the most significant species) could affect epiphytic algae, particularly in Lake Krzczeń, with the highest fish abundance.…”

“…Furthermore, a meta-analysis of 85 experimental studies showed that grazing by invertebrates on algae were found to be greater than nutrient effects (Hillebrand, 2002). In general, the reports on the role of zooplankton and fish in shaping epiphyton communities are scarce and mostly experimental (Tall et al, 2006;Abe et al, 2007;Blanco et al, 2008;Guariento et al, 2010). Some anthropogenic disturbances, like man-made water level fluctuations (WLFs), eutrophication or water pollution are also important factors that influence epiphyton (Barbour et al, 1999;Kernan et al, 2010;Pfeiffer et al, 2015).…”