Feces from Piscivorous and Herbivorous Birds Stimulate Differentially Phytoplankton Growth

Abstract

Aquatic birds may impact shallow ecosystems via organic and nutrient enrichment with feces. Such input may alleviate nutrient limitation, unbalance their ecological stoichiometry, and stimulate primary production. Herbivorous and piscivorous birds may produce different effects on aquatic ecosystems due to different physiology, diet and feces elemental composition. We analyze the effects of droppings from swans (herbivorous) and cormorants (piscivorous) on phytoplankton growth via a laboratory experiment. These birds are well represented in the Curonian Lagoon, where they form large colonies. As this lagoon displays summer algal hyper-blooms, we hypothesize an active, direct role of birds via defecation on algal growth. Short-term incubations of phytoplankton under low and high feces addition produces different stimulation of algal growth, significantly higher with high inputs of cormorant feces. The latter produces a major effect on reactive phosphorus concentration that augments significantly, as compared to treatments with swan feces, and determines an unbalanced, N-limited stoichiometry along with the duration of the experiment. During the incubation period, the dominant algal groups switch from blue-green to green algae, but such switch is independent of the level of feces input and from their origin. Heterotrophic bacteria also are stimulated by feces addition, but their increase is transient.

Seabird influence on ecological processes in coastal marine ecosystems: An overlooked role? A critical review

“…P and N are the major limiting nutrients for primary production in most aquatic ecosystems (Smith, 2006), hence the increase of ornithogenic nutrients can lead to important shifts in primary production patterns in the recipient area, generally fostering phytoplankton growth (Methratta, 2004;Petkuviene et al, 2019;Shatova et al, 2016;Signa et al, 2012). In particular, a shift from oligotrophic to eutrophic state and from benthic to planktonic production has been observed in temperate coastal ponds subject to guano runoff, due to the rapid phytoplankton nutrient uptake and bloom followed by decreased light availability for benthic macrophytes and further reduced benthic production (Signa et al, 2012).…”

“…System typology where the effects have been found, and related references, are also showed. ecological process main effect system typology reference a) resource linkage nutrient input increase in nutrient load coastal ponds, estuaries Portnoy 1990;Bildstein et al 1992 changes in nutrient cycling rocky shores Ganning and Wulff 1969;Golovkin and Garkavaya1975 change in water and sediment chemistry (high pH, chlorophyll-a and nutrient concentrations) coastal ponds Weber et al 2006;Keatley et al 2009;Signa et al 2012;Duda et al 2018 coral reefs Honig and Mahoney 2016;Lorrain et al 2017 bottom-up control on primary producers increase in phytoplankton production tidepools, coastal ponds Methratta 2004, Signa et al 2012, Shatova et al 2016, Petkuviene et al 2019 change in macroalgae community composition (shift from perennial to opportunistic species) rocky shores Wootton 1991;Kolb et al 2010;Gagnon et al 2016 species shift and increase in macrophyte biomass estuaries Powell et al 1991 Hamilton et al 2006;Cheverie et al 2014;Gagnon et al 2016 predatory pressure of cormorants potential conflicts with human fishing activities lagoons and fish ponds Leopold et al 1998, Hobson 2009, Vetemaa et al 2010, Steffens 2011 limited conflicts with human fishing activities due to niche and size segregation of fish stock Žydelis and Kontautas 2008;Doucette et al 2011;Troynikov et al 2013…”

Understanding anthropogenic impacts on zoogeochemistry is essential for ecological restoration

“…For example, stoichiometric differences in the diet of large vertebrate browsers and grazers lead to stoichiometric differences in their resource subsidies (feces), which can ultimately influence competitive advantages between N 2 ‐fixing trees and grasses (Sitters & Olde Venterink 2021). Similarly, differences in the fecal stoichiometry of piscivorous and herbivorous birds have shown to differentially stimulate phytoplankton growth in freshwater systems (Petkuviene et al 2019), while greater demands for P and calcium (Ca) to support larger bone structures may also modify resource subsidies by larger animals (le Roux et al 2020).…”

Biological Indicators for Fecal Pollution Detection and Source Tracking: A Review

“…Birds can also heavily impact water systems. For example, cormorant defecation in shallow-water ecosystems can lead to algal bloom formation [44]. Defecation by a small cormorant population may not have a significant impact, but a group living in large colonies makes their feces quantitatively relevant as a nutrient input.…”