Phosphorus flux by macrobenthic invertebrates in a shallow eutrophic lake Donghu: spatial change

Abstract

We estimated phosphorus flux mediated by benthic invertebrates from the sediments to the water in a shallow eutrophic lake (lake Donghu, central China) and quantified spatial (littoral and central sites) and specific (among different benthic taxa) differences. The mass-specific excretion rates of phosphorus (soluble reactive phosphorus (SRP, ηmol·mg dry mass -1 ·h -1 ) by benthic invertebrates (abundant taxa) were estimated experimentally and calculated as a final minus of initial nutrient mass divided by dry mass of organisms. Results showed high importance of chironomid larvae as a contributor to the total P flux from sediments to water in shallow lake Donghu. Benthic biomass (from 0.002 to 32.8 g dry mass·m -2 ) distribution and species composition (31 taxa) were studied (October 2009) in three regions of lake Donghu (Guozhenghu, Miaohu, Yujiahu) using samples from three depths: the shallow littoral site (0.2-1 m depth), central site with 2 m depth, and central site with more than 3 m depth. The total estimated SRP excretion by benthic invertebrate reaches 36% of the direct SPR flux from sediments to water in this lake. The phosphorus regeneration by benthic animals is the most intensive in the shallow littoral sites (69.5 µmol P·m -2 ·day -1 ) and at least 20 times greater than in central sites (3.4 µmol P·m -2 ·day -1 ) of lake Donghu. The results support notable differences in the SRP excretion rates between taxa and sites. The spatial difference in the SRP flux might be considered as a general feature of lakes with periodical changing oxygen near bottom. RÉSUMÉFlux de phosphore dû aux invertébrés macrobenthiques dans un lac peu profond et eutrophe, le lac Donghu.Nous avons estimé le flux de phosphore des sédiments vers l'eau créé par les invertébrés benthiques dans un lac peu profond eutrophe (lac Donghu, centre de la Chine) et quantifié les différences spatiales (sites du littoral et du centre) et spéci-fiques (entre différents taxons benthiques). Les taux d'excrétion du phosphore (phosphore réactif soluble : SRP, ηmol·mg de masse sèche -1 ·h -1 ) par les invertébrés Mots-clés :phosphore, excrétion, zoobenthos, Knowledge and Management of Aquatic Ecosystems (2011) 402, 11 © ONEMA, 2011 http://www.kmae-journal.org DOI: 10.1051/kmae/2011073 L. Ji et al.: Knowl. Managt. Aquatic Ecosyst. (2011 11p2 benthiques (taxons abondants) ont été estimés expérimentalement et calculés comme la différence entre masses de nutriment finale et initiale divisée par la masse sèche des organismes. Les résultats ont montré une grande importance des larves de chironomides en tant que contributeurs au flux de P total de sédiments vers l'eau dans le lac peu profond Donghu. La distribution de la biomasse benthique (de 0,002 à 32,8 g de matière sèche·m -2 ) et sa composition spécifique (31 taxons) ont été étudiées (octobre 2009) dans trois régions du lac Donghu (Guozhenghu, Miaohu, Yujiahu) en utilisant des échantillons provenant de trois profondeurs : le site peu profond du littoral (0,2-1 m de profondeur), le site c...

Macroinvertebrate communities in the Big East Lake water network in relation to environmental factors

“…Due to water pollution and the loss of diverse habitat, the species richness of mollusks sharply decreased in the DH. For instance, 41 mollusks were found in 1960s (Chen et al, 1975), 15 mollusks in 1970s (Chen and Liang, 1980), 3 mollusks in 1997-1999 (Gong et al, 2000), 8 mollusks in 2008 (Wang et al, 2010), 7 mollusks in 2009 (Ji et al, 2011) and only 6 mollusks in our study. Focusing on the whole macroinvertebrates in the DH, based on the incomplete statistical results, the species richness decreased from 133 in 1960s to 67 in 1990s with sharply declining due to high anthropogenic pressure (Wang, 2005).…”

“…dominated the communities in all seasons. In comparison with the historical data, the composition of dominant species in the BELWN almost unchanged, mainly including L. hoffmeisteri, Tanypus sp., Chironomus sp., B. aeruginosa and B. sowerbyi (Wang et al, 2010;Ji et al, 2011). At present stage, most of lakes in the BELWN have become phytoplankton-dominated lakes from macrophytic lakes.…”

“…The BELWN was no exception to have high seasonal variation in standing crops, it was related to the differences in growth rate of difference species in difference seasons (Cowell and Vodopich, 1981;Chen and Wang, 1982). Studies showed under normal conditions the dominant groups of macroinvertebrates in the urban lakes and eutrophic lakes were mainly composed of high-density oligochaetes and chironomids (Gong et al, 2000;Ji et al, 2011;Liu et al, 2013). As an urban lake system, the BELWN conformed with the above-mentioned rules, with high percentages of chironomids in summer, autumn and winter (68.74%, 57.30%, 63.14%) and big percent of oligochaetes in spring (84.12%).…”

“…Due to transportation and farming, the DH is divided into several lakelets, including Shuiguohu lake (SGH), Tanglinghu lake (TLH), Shaoqihu lake (SQH), Guozhenghu lake (GZH), Tuanhu lake (TH), Houhu lake (HH), Miaohu lake (MH) and Yujiahu lake (YJH). And the SH is divided into inner lake and outer lake (Wang et al, 2010;Yan and Li, 2010;Ji et al, 2011;Lei and Jiang, 2012) (Fig. 1).…”

“…Macroinvertebrates play a critical role in the natural flow of energy and nutrients in aquatic system (Gong et al, 2000;Ji et al, 2011Ji et al, , 2015, and are ideal biological indicators to monitor and assess ecological status due to their relatively weak migration ability, long life cycles and different tolerance to stressors (Covich et al, 1999;Beck and Hatch, 2009). The macroinvertebrates in the BELWN were frequently investigated, mainly focusing on community structure (Wang, 1996;Kuang et al, 1997;Gong et al, 2000;Gong, 2002;Wu et al, 2005;Wang, 2009;Wang et al, 2010;Cai et al, 2013;Hu et al, 2014).…”