Goose-mediated nutrient enrichment and planktonic grazer control in arctic freshwater ponds

Abstract

A dramatic increase in the breeding population of geese has occurred over the past few decades at Svalbard. This may strongly impact the fragile ecosystems of the Arctic tundra because many of the ultra-oligotrophic freshwater systems experience enrichment from goose feces. We surveyed 21 shallow tundra ponds along a gradient of nutrient enrichment based on exposure to geese. Concentrations of total phosphorus (P) and dissolved inorganic nitrogen (DIN) in the tundra ponds ranged from 2-76 to 2-23 g l ¡1 respectively, yet there was no signiWcant increase in phytoplankton biomass (measured as chlorophyll a; range: 0.6-7.3 g l ¡1 ) along the nutrient gradient. This lack of response may be the result of the trophic structure of these ecosystems, which consists of only a two-trophic level food chain with high biomasses of the eYcient zooplankton grazer Daphnia in the absence of Wsh and scarcity of invertebrate predators. Our results indicate that this may cause a highly eYcient grazing control of phytoplankton in all ponds, supported by the fact that large fractions of the nutrient pools were bound in zooplankton biomass. The median percentage of Daphnia-N and Daphnia-P content to particulate (sestonic) N and P was 338 and 3009%, respectively, which is extremely high compared to temperate lakes. Our data suggest that Daphnia in shallow arctic ponds is heavily subsidized by major inputs of energy from other food sources (bacteria, benthic bioWlm), which may be crucial to the persistence of strong top-down control of pelagic algae by Daphnia.

Case study on the efficacy of a lanthanum-enriched clay (Phoslock®) in controlling eutrophication in Lake Het Groene Eiland (The Netherlands)

“…Faeces analysis revealed mean PO 4 -P concentrations of 2 mg g -1 dry feces, which is in agreement with the literature data on geese droppings (Van Geest et al, 2007;Ayers et al, 2010). Assuming that a Canada goose daily produces 80 g dry weight of droppings (Scherer et al, 1995), then on average, daily more than 4 kg of droppings are produced around the lake.…”

Nutrient Uptake and Short-Term Responses of Phytoplankton and Benthic Algal Communities from a Subarctic Pond to Experimental Nutrient Enrichment in Microcosms

“…WAP 20 is very shallow (<0.5 m), has sparse macrophytes, and so the luxuriant benthic mat along the pond bottom has potential to contribute a large fraction of the pond's total primary production. We note that lower-thanexpected phytoplankton chlorophyll a concentrations have been found in other Arctic lakes and ponds and attributed to benthic productivity (e.g., Van Geest et al, 2007;Côté et al, 2010). Moreover, a recent nutrient enrichment experiment that used microcosms containing water from a nearby coastal fen pond, with and without surficial pond sediments and associated benthic algal mat, demonstrated that these ponds rapidly assimilate additions of dissolved inorganic N (nitrate, ammonia) and P (phosphate) when surficial sediments and associated benthic biofilm are present (Eichel et al, 2014).…”

“…For over 20 years, concerns have been mounting about the environmental effects of increased waterfowl populations and how changes in their geographic distribution may alter the structure and function of Arctic and subarctic freshwater ecosystems. Consequences may include eutrophication, changes in nutrient cycling, and destruction of vegetation and available habitat (e.g., Handa et al, 2002;Gregory-Eaves et al, 2004;Lim et al, 2005;Van Geest et al, 2007;Côté et al, 2010;Sun et al, 2013).…”

Maximizing growth rate at low temperatures: RNA:DNA allocation strategies and life history traits of Arctic and temperate Daphnia

“…Consequently, polyploid Arctic organisms will have an increased demand for P, which may be constrained by low P content of the food, especially in generally nutrient-poor Arctic ponds (Van Geest et al 2007). Therefore, it can be expected that selection should favour some P-sparing mechanisms, as the animal that develops fastest per unit P used will be favoured in competition (Elser et al 1996;Hessen et al 2008).…”