Open Lake Phosphorus Forcing of <i>Cladophora</i> Growth: Modeling the Dual Challenge in Great Lakes Trophic State Management
Stimulated by excess levels of phosphorus, the attached, filamentous green alga <i>Cladophora</i> grows to nuisance proportions in Lake Michigan, one of the Laurentian Great Lakes. While nearshore waters impacted by local sources of the nutrient continue to support nuisance conditions, o...
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| Format: | Article |
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MDPI AG
2021-09-01
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| Series: | Water |
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| Online Access: | https://www.mdpi.com/2073-4441/13/19/2680 |
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| author | Xing Zhou Martin T. Auer Pengfei Xue |
| author_facet | Xing Zhou Martin T. Auer Pengfei Xue |
| author_sort | Xing Zhou |
| collection | DOAJ |
| description | Stimulated by excess levels of phosphorus, the attached, filamentous green alga <i>Cladophora</i> grows to nuisance proportions in Lake Michigan, one of the Laurentian Great Lakes. While nearshore waters impacted by local sources of the nutrient continue to support nuisance conditions, offshore waters have undergone oligotrophication in response to reductions in phosphorus loading and benthification of phosphorus cycling by invasive dreissenid mussels. A concept termed the Dual Challenge recognizes that implementation of more stringent phosphorus-loading objectives (to control <i>Cladophora</i> in the nearshore) stands in conflict with a foreseen need to mitigate oligotrophication in the offshore (to sustain a healthy fishery). Attention to this nearshore–offshore dynamic calls into play the role of cross-margin phosphorus transport in mediating both endmembers of the conflict. We applied a biophysical model simulating soluble reactive (SRP) and particulate (PP) phosphorus, mussel biokinetics, and cross-margin mass transport in addressing the Dual Challenge. Pre- and post-dreissenid monitoring results suggest that a reduction in offshore PP levels (food web nutrition) in excess of 40% (2.4 to 1.4 mgP·m<sup>−3</sup>) has driven oligotrophication and attendant food web dysfunction. Yet, in the absence of local sources, model-predicted nearshore SRP levels remain at or below those required to prevent nuisance growth. These findings indicate that there is a margin of ~1 mgP·m<sup>−3</sup> over which offshore PP levels could be increased (to the benefit of the food web and the fishery) without hindering efforts to reduce nuisance algal growth through local source control. |
| first_indexed | 2024-03-10T06:48:02Z |
| format | Article |
| id | doaj.art-420d87b04bbc4787819857cfec7c78a0 |
| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-10T06:48:02Z |
| publishDate | 2021-09-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Water |
| spelling | doaj.art-420d87b04bbc4787819857cfec7c78a02023-11-22T17:00:56ZengMDPI AGWater2073-44412021-09-011319268010.3390/w13192680Open Lake Phosphorus Forcing of <i>Cladophora</i> Growth: Modeling the Dual Challenge in Great Lakes Trophic State ManagementXing Zhou0Martin T. Auer1Pengfei Xue2Department of Civil, Environmental, and Geospatial Engineering and Great Lakes Research Center, Michigan Technological University, Houghton, MI 49931, USADepartment of Civil, Environmental, and Geospatial Engineering and Great Lakes Research Center, Michigan Technological University, Houghton, MI 49931, USADepartment of Civil, Environmental, and Geospatial Engineering and Great Lakes Research Center, Michigan Technological University, Houghton, MI 49931, USAStimulated by excess levels of phosphorus, the attached, filamentous green alga <i>Cladophora</i> grows to nuisance proportions in Lake Michigan, one of the Laurentian Great Lakes. While nearshore waters impacted by local sources of the nutrient continue to support nuisance conditions, offshore waters have undergone oligotrophication in response to reductions in phosphorus loading and benthification of phosphorus cycling by invasive dreissenid mussels. A concept termed the Dual Challenge recognizes that implementation of more stringent phosphorus-loading objectives (to control <i>Cladophora</i> in the nearshore) stands in conflict with a foreseen need to mitigate oligotrophication in the offshore (to sustain a healthy fishery). Attention to this nearshore–offshore dynamic calls into play the role of cross-margin phosphorus transport in mediating both endmembers of the conflict. We applied a biophysical model simulating soluble reactive (SRP) and particulate (PP) phosphorus, mussel biokinetics, and cross-margin mass transport in addressing the Dual Challenge. Pre- and post-dreissenid monitoring results suggest that a reduction in offshore PP levels (food web nutrition) in excess of 40% (2.4 to 1.4 mgP·m<sup>−3</sup>) has driven oligotrophication and attendant food web dysfunction. Yet, in the absence of local sources, model-predicted nearshore SRP levels remain at or below those required to prevent nuisance growth. These findings indicate that there is a margin of ~1 mgP·m<sup>−3</sup> over which offshore PP levels could be increased (to the benefit of the food web and the fishery) without hindering efforts to reduce nuisance algal growth through local source control.https://www.mdpi.com/2073-4441/13/19/2680<i>Cladophora</i>phosphorusdreissenid musselscross margin transportGreat Lakesoligotrophication |
| spellingShingle | Xing Zhou Martin T. Auer Pengfei Xue Open Lake Phosphorus Forcing of <i>Cladophora</i> Growth: Modeling the Dual Challenge in Great Lakes Trophic State Management Water <i>Cladophora</i> phosphorus dreissenid mussels cross margin transport Great Lakes oligotrophication |
| title | Open Lake Phosphorus Forcing of <i>Cladophora</i> Growth: Modeling the Dual Challenge in Great Lakes Trophic State Management |
| title_full | Open Lake Phosphorus Forcing of <i>Cladophora</i> Growth: Modeling the Dual Challenge in Great Lakes Trophic State Management |
| title_fullStr | Open Lake Phosphorus Forcing of <i>Cladophora</i> Growth: Modeling the Dual Challenge in Great Lakes Trophic State Management |
| title_full_unstemmed | Open Lake Phosphorus Forcing of <i>Cladophora</i> Growth: Modeling the Dual Challenge in Great Lakes Trophic State Management |
| title_short | Open Lake Phosphorus Forcing of <i>Cladophora</i> Growth: Modeling the Dual Challenge in Great Lakes Trophic State Management |
| title_sort | open lake phosphorus forcing of i cladophora i growth modeling the dual challenge in great lakes trophic state management |
| topic | <i>Cladophora</i> phosphorus dreissenid mussels cross margin transport Great Lakes oligotrophication |
| url | https://www.mdpi.com/2073-4441/13/19/2680 |
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