Ecological studies on the decomposition rate of fish carcasses by benthic organisms in the littoral zone of Lake Constance, Germany

Abstract

-Using field experiments, we investigated the effects of fish carcasses (so called 'food falls') on benthic fauna. We simulated food falls using freshly killed fish during two different seasons (spring and summer) in the littoral zone of a large, pre-alpine meso-oligotrophic lake in central Europe (Lake Constance, Germany). This study provides evidence that input in the form of fish carcasses may play an important role in nutrient dynamics within this ecosystem. The benthic communities in the vicitinity and underneath the food fall were strongly influenced by the food fall. The results show that this supply of organic matter has a significant influence on the relationships within the communities, which are clearly dominated by bacteria, followed by copepod nauplii, cyclopoid copepods, chironomids, and ostracods. Total decomposition was obtained between days 80 and 68 of the experiments. The food fall had a positively but not significant effect on meiofaunal assemblages in these experiments. Furthermore, the results showed a negative relationship between bacteria and meiofauna abundance, indicating grazing by the meiobenthos on the bacterial community. These findings support other studies that found that the meiofauna exerted a grazing pressure on the microbial community, where this process was important in the decomposition of carcasses. Moreover, this study shows the potential importance of fish carcasses in Lake Constance, where food falls may generate high abundances and diversity of the benthic fauna and support high bacterial activities in this littoral ecosystem.

When are fish sources vs. sinks of nutrients in lake ecosystems?

“…This can be viewed as a special facet of nutrient sequestration into the animal pool (the first example), except in this case nutrients are stored in carcasses instead of living individuals. There is debate as to how quickly nutrients are mineralized from fish carcasses, especially P from P-rich bones and scales (Schenau and De Lange 2000, Chidami and Amyot 2008, Premke et al 2010.…”

“…Scavenging animals may rapidly consume fish carcasses, especially at shallow depths (Chidami and Amyot 2008, Janetski et al 2009, Premke et al 2010. However, as with piscivores, scavengers are unlikely to be a longterm ecosystem-level P via a long-term biomass increase.…”

Meiobenthic community underneath the carcass of a stingray: a snapshot after natural death

“…Other taxa, such as acari and poly chaetes, were found only once (as singletons in only 1 sample) under the stingray carcass, but otherwise were re stricted to samples outside the carcass. As ob served for other aquatic systems (Debenham et al 2004, Pavlyuk et al 2009, Premke et al 2010, the encountered stingray carcass had a negative impact on meio faunal abundances. Such a negative impact is probably due in part to hypoxia and the presence of toxic sulfides in sediments underneath the carcass, since most of the affected taxa (i.e.…”

“…Larger scavengers, like starfish, fish and amphipods can consume large amounts of food falls in < 5 d (Kaiser & Moore 1999). However, microbial decomposition is much slower, taking several weeks to months, depending on the local conditions, to completely decompose a fish carcass (Minshall et al 1991, Parmenter & Lamarra 1991, Fenoglio et al 2005, Premke et al 2010). This much slower decomposition is partly due to the fact that scavenger microbes produce noxious chemicals that deter animal scavengers (Burkepile et al 2006).…”

The fate of phosphorus in decomposing fish carcasses: a mesocosm experiment

“…Similarly, Premke et al . () reported total decomposition of fish carcasses after 2–3 months in the pre‐alpine Lake Constance, Germany (water temperature ranged between 4 and 25 °C). In contrast, Kitchell et al .…”