Suspended particulates decline along a dense mussel bed in a small Minnesota stream, U.S.A.

Water filtration by freshwater mussels (Bivalvia: Unionidae) is a valued ecosystem service; however, it has not been well studied in natural settings. To examine the potential influence of mussel filtration on suspended particulates, we measured the concentration of Escherichia coli, chlorophyll-a, and total suspended solids along a stream reach with a dense mussel assemblage (Mussel Site) and a stream reach with no mussels (Reference Site) within the Saint Croix watershed in Minnesota, U.S.A. We predicted that these particulates would exhibit a greater decline at the Mussel Site compared to the Reference Site because of mussel filtration. We collected three replicate water samples at upstream, midpoint, and downstream stations at both sites in August, September, and October 2022 to measure concentration values. In accordance with our predictions, concentrations of particulates declined more prominently from upstream to downstream at the Mussel Site than at the Reference Site. Linear mixed-effect models indicated that the interaction between mussel presence (Mussel Site, Reference Site) and sample location (upstream, midpoint, downstream) best explained these patterns. There was lower support for the total suspended solids interactive model compared to the other two particulates. Mussels selectively feeding on organic rather than inorganic particles may help to explain the lower support of the total suspended solids model. Our results suggest that mussels can appreciably reduce suspended particulate concentrations including harmful bacteria. This study provides a useful example of the ecosystem services mussels provide and why their conservation is needed. The Sunrise River, our mussel site, had an average density of 43.9 mussels/m2 +3.5 SE and an estimated 829,146 mussels + 66,552 SE across its length (715 m). Seventeen species were collected, with Ortmanniana ligamentina making up 77.3% of the assemblage.Our results suggest that mussel filtration reduced concentrations of E. coli, total suspended solids, and chlorophyll-a.This study provides a useful example of why mussel conservation is important for water quality. The Sunrise River, our mussel site, had an average density of 43.9 mussels/m2 +3.5 SE and an estimated 829,146 mussels + 66,552 SE across its length (715 m). Seventeen species were collected, with Ortmanniana ligamentina making up 77.3% of the assemblage. Our results suggest that mussel filtration reduced concentrations of E. coli, total suspended solids, and chlorophyll-a. This study provides a useful example of why mussel conservation is important for water quality.

淡水贻贝（双壳纲：Unionidae）的滤水作用是一项极具价值的生态系统服务，但目前在自然生境中对其的研究仍不够充分。为探究贻贝滤水作用对悬浮颗粒物的潜在影响，我们于美国明尼苏达州圣克罗伊流域内，选取了贻贝密集群落分布的河段（贻贝样地）与无贻贝分布的河段（对照样地），对其中的大肠埃希氏菌(Escherichia coli)、叶绿素a以及总悬浮颗粒物浓度开展了测定。我们预测，相较于对照样地，贻贝样地内的此类颗粒物浓度会出现更显著的下降，这一效应源于贻贝的滤食作用。2022年8、9、10月，我们在两个样地的上游、中游及下游站位分别采集了三份平行水样，以测定各目标物质的浓度。实验结果与我们的预测相符：相较于对照样地，贻贝样地中颗粒物浓度从上游至下游的下降幅度更为显著。线性混合效应模型分析显示，贻贝存在与否（贻贝样地、对照样地）与采样站位（上游、中游、下游）的交互作用，能够最好地解释上述观测模式。相较于另外两类颗粒物，总悬浮颗粒物的交互模型拟合度较低。贻贝对有机颗粒物而非无机颗粒物的选择性取食，或可解释这一现象。我们的研究结果表明，贻贝可显著降低包括致病细菌在内的悬浮颗粒物浓度。本研究清晰展现了贻贝所提供的生态系统服务，也阐明了对其进行保护的必要性。本研究的贻贝样地为日出河(Sunrise River)，其河段总长715米，贻贝平均密度为43.9只/平方米（标准误±3.5），估算总种群数量为829146只（标准误±66552）。本次调查共采集到17个贻贝物种，其中Ortmanniana ligamentina占群落组成的77.3%。我们的研究结果表明，贻贝滤水作用可降低大肠埃希氏菌、总悬浮颗粒物及叶绿素a的浓度。本研究为阐释贻贝保护对水质保护的重要性提供了极具参考价值的实例。本研究的贻贝样地为日出河(Sunrise River)，其河段总长715米，贻贝平均密度为43.9只/平方米（标准误±3.5），估算总种群数量为829146只（标准误±66552）。本次调查共采集到17个贻贝物种，其中Ortmanniana ligamentina占群落组成的77.3%。我们的研究结果表明，贻贝滤水作用可降低大肠埃希氏菌、总悬浮颗粒物及叶绿素a的浓度。本研究为阐释贻贝保护对水质保护的重要性提供了极具参考价值的实例。