A food web modeling analysis of a Midwestern, USA eutrophic lake dominated by non-native Common Carp and Zebra Mussels

Abstract

Food web modeling is recognized as fundamental to understanding the complexities of aquatic systems.Ecopath is the most common mass-balance model used to represent food webs and quantify trophic inter-actions among groups. We constructed annual Ecopath models for four consecutive years during the firsthalf-decade of a zebra mussel invasion in shallow, eutrophic Clear Lake, Iowa, USA, to evaluate changesin relative biomass and total system consumption among food web groups, evaluate food web impactsof nonnative common carp and zebra mussels on food web groups, and to interpret food web impactsin light of ongoing lake restoration. Total living biomass increased each year of the study; the majorityof the increase due to a doubling in planktonic blue green algae, but several other taxa also increasedincluding a more than twoorder of magnitude increase in zebra mussels. Common carp accounted for thelargest percentage of total fish biomass throughout the study even with on-going harvest. Chironomids,common carp, and zebra mussels were the top-three ranking consumer groups. Non-native commoncarp and zebra mussels accounted for an average of 42% of the total system consumption. Despite the rel-atively high biomass densities of common carp and zebra mussel, food web impacts was minimal due toexcessive benthic and primary production in this eutrophic system. Consumption occurring via benthicpathways dominated system consumption in Clear Lake throughout our study, supporting the argumentthat benthic food webs are significant in shallow, eutrophic lake ecosystems and must be considered ifecosystem-level understanding is to be obtained. Keywords: Ecopath Zebra mussels Dreissena polymorpha Common carp Cyprinus carpio Non-native Trophic interactions Lake restoration a b s t r a c t Food web modeling is recognized as fundamental to understanding the complexities of aquatic systems. Ecopath is the most common mass-balance model used to represent food webs and quantify trophic interactions among groups. We constructed annual Ecopath models for four consecutive years during the first half-decade of a zebra mussel invasion in shallow, eutrophic Clear Lake, Iowa, USA, to evaluate changes in relative biomass and total system consumption among food web groups, evaluate food web impacts of non-native common carp and zebra mussels on food web groups, and to interpret food web impacts in light of on-going lake restoration. Total living biomass increased each year of the study; the majority of the increase due to a doubling in planktonic blue green algae, but several other taxa also increased including a more than two-order of magnitude increase in zebra mussels. Common carp accounted for the largest percentage of total fish biomass throughout the study even with on-going harvest. Chironomids, common carp, and zebra mussels were the top-three ranking consumer groups. Non-native common carp and zebra mussels accounted for an average of 42% of the total system consumption. Despite the relatively high biomass densities of common carp...

Benthification, biotic homogenization behind the trophic downgrading in altered ecosystems

“…The common carp (C. carpio) is a common invader included in other omnivores in our approach (see Material and Methods). critical than tilapias as ecosystem engineers (Estes et al 2011) and omnivore-planktivore species in shallow reservoirs worldwide (Liu et al 2007, Matsuzaki et al 2009, Colvin et al 2015). 7.…”

“…Otherwise, an increase in the mean turbidity from this interaction indicates an ecosystem effect. critical than tilapias as ecosystem engineers (Estes et al 2011) and omnivore-planktivore species in shallow reservoirs worldwide (Liu et al 2007, Matsuzaki et al 2009, Colvin et al 2015). An occasional spillover of these fish downstream threatens ecosystems given the role of M. salmoides as a keystone group (Blois et al 2013, Pinnegar et al 2014.…”

A food web modeling assessment of Asian Carp impacts in the Middle and Upper Mississippi River, USA

“…Ecopath with Ecosim (EwE) is a food web modeling software suite available for free download (www.ecopath.org) and commonly used to construct mass-balance trophic models (Christensen and Walters, 2004;Colleter et al, 2015). While primarily used to model marine ecosystems, published models of freshwater systems are becoming more prevalent (e.g., Colvin et al, 2015;Zhang et al, 2016). All models in this study were constructed in EwE version 6.4.4.12634.…”

Fish Growth Changes over Time in a Midwestern U.S. Lake

“…Clear Lake has undergone significant changes in the past and is poised to change rapidly in the future. A 4-year food web modeling study highlighted large changes in biomass and trophic pathways during 2007-2010 associated with the roles of nonnative Common Carp, invading zebra mussels, and phytoplankton dynamics, all in the context of multiple management actions (Colvin et al 2015). The most recent (2005)(2006)(2007) of the annual growth rates measured in the present study occurred during the first few years of the zebra mussel invasion in Clear Lake, which may have been sufficient to allow glimpses of the eventual effects zebra mussels will have, but was not sufficient to permit a rigorous analysis of zebra mussel impacts.…”