Many taxa of North American unionid mussels are imperiled due to biofouling by invasive dreissenid mussels. Here, we report on biofouling rates of unionid mussels suspended in cages during the growing season in nearshore embayments in Lake Erie (2013-2016), Lake Michigan (Green Bay 2016, Grand Traverse Bay 2015) and Lake Huron (Saginaw Bay 2015). Mussels were deployed in early summer (late May or early June) and retrieved in late summer or fall (late August or early September). Wet weights were collected from mussels before and after removal of biofouling taxa (primarily dreissenid mussels).

Invasion of North American waters by Dreissena polymorpha and D. rostriformis bugensis has resulted in declines in native North American Unionoida mussels. Dreissenid mussels biofoul unionid mussels in large numbers and interfere with unionid movement, acquisition of food and ability to open and close their shells. Initial expectations for the Great Lakes were that unionids would be extirpated where they co-occur with dreissenids, but recently adult and juvenile unionids have been found alive in several apparent refugia. These unionid populations may persist due to reduced dreissenid biofouling in these areas, and/or due to processes that remove biofoulers. For example, locations inaccessible to veligers may reduce biofouling and habitats with soft substrates may allow unionids to burrow and thus remove dreissenids. Here, biofouling was measured by deploying caged unionid mussels (Lampsilis siliquoidea) at 36 sites across the western basin of Lake Erie to assess spatial variation in biofouling and to identify other areas that might promote the persistence or recovery of native unionid mussels. Biofouling ranged from 0.03 – 26.33 g per mussel, reached a maximum in the immediate vicinity of the Maumee rivermouth, and appeared to primarily consist of dreissenid mussels. A known mussel refugium in the vicinity of a power plant near the Maumee rivermouth actually exhibited very high biofouling rates, suggesting low dreissenid colonization is unlikely to be the primary cause of unionid survival in this refugium. The southern nearshore area of Lake Erie, near another refugium, also had very low biofouling. A large stretch of the western basin appeared to have low biofouling rates and muddy substrates, raising the possibility that these open water areas could support remnant and returning populations of unionid mussels.

Invasion of North American waters by Dreissena polymorpha and D. rostriformis bugensis has resulted in declines in native North American Unionoida mussels. Dreissenid mussels biofoul unionid mussels in large numbers and interfere with unionid movement, acquisition of food and ability to open and close their shells. Initial expectations for the Great Lakes were that unionids would be extirpated where they co-occur with dreissenids, but recently adult and juvenile unionids have been found alive in several apparent refugia. These unionid populations may persist due to reduced dreissenid biofouling in these areas, and/or due to processes that remove biofoulers. For example, locations inaccessible to veligers may reduce biofouling and habitats with soft substrates may allow unionids to burrow and thus remove dreissenids. Here, biofouling was measured by deploying caged unionid mussels (Lampsilis siliquoidea) at 36 sites across the western basin of Lake Erie to assess spatial variation in biofouling and to identify other areas that might promote the persistence or recovery of native unionid mussels. Biofouling ranged from 0.03 – 26.33 g per mussel, reached a maximum in the immediate vicinity of the Maumee rivermouth, and appeared to primarily consist of dreissenid mussels. A known mussel refugium in the vicinity of a power plant near the Maumee rivermouth actually exhibited very high biofouling rates, suggesting low dreissenid colonization is unlikely to be the primary cause of unionid survival in this refugium. The southern nearshore area of Lake Erie, near another refugium, also had very low biofouling. A large stretch of the western basin appeared to have low biofouling rates and muddy substrates, raising the possibility that these open water areas could support remnant and returning populations of unionid mussels.

Survival and growth of four species of juvenile mussels in a pulsed flow-through auto-feeding beaker system.

Survival and growth of four species of juvenile mussels in a pulsed flow-through auto-feeding beaker system.

The Hudson River, New York, was contaminated with polychlorinated biphenyls (PCBs) from two General Electric plants over a period of ~30 years and PCBs are still present in sediment and biota today. The river provides habitat for a variety of plants and animals, including native freshwater mussels. Although little is known about mussels in this river, managers were concerned that a 7-year remediation program to remove PCB-contaminated sediments could affect mussels. From 2013-2019, we conducted stratified (non-remediated, before remediation, after remediation) quantitative surveys across 17-pool-stratum combinations across nine pools. Sampling was done during August through October of each year. At each site, divers excavated sediment from two 0.063 square meter quadrats on the riverbed. Divers excavated substrates to a depth of about 15 centimeters and placed material from both quadrats into a 6-millimeter mesh bag. Mussels were sorted from the sediments, identified to species, aged by counting external annuli, and measured for shell length. These data were used to generate estimates of species composition, density, size, structure, and ecosystem services of mussel assemblages pre- and post-remediation.

The Hudson River, New York, was contaminated with polychlorinated biphenyls (PCBs) from two General Electric plants over a period of ~30 years and PCBs are still present in sediment and biota today. The river provides habitat for a variety of plants and animals, including native freshwater mussels. Although little is known about mussels in this river, managers were concerned that a 7-year remediation program to remove PCB-contaminated sediments could affect mussels. From 2013-2019, we conducted stratified (non-remediated, before remediation, after remediation) quantitative surveys across 17-pool-stratum combinations across nine pools. Sampling was done during August through October of each year. At each site, divers excavated sediment from two 0.063 square meter quadrats on the riverbed. Divers excavated substrates to a depth of about 15 centimeters and placed material from both quadrats into a 6-millimeter mesh bag. Mussels were sorted from the sediments, identified to species, aged by counting external annuli, and measured for shell length. These data were used to generate estimates of species composition, density, size, structure, and ecosystem services of mussel assemblages pre- and post-remediation.

This data set includes mortality data from acute toxicity tests with juveniles of the mussel, Lampsilis siliquoidea exposed to 6PPD and 6PPDQ. Concurrently collected analytical chemistry and general water quality measurements are included.

This data set contains toxicity data from short term 7-day chronic water-only bioassays to assess the effects pH on ammonia toxicity to survival and growth of a juvenile fatmucket mussel (Lampsilis siliquoidea). We conducted 4 concurrent exposures at nominal pHs of 7.0, 7.5, 8.0, and 8.5 with varying ranges of ammonia to capture effect concentrations. This data set has three tables: (1) routine water quality, including measured pH and ammonia (2) survival and dry weight of juvenile mussels, and (3) length measurements of juvenile mussels

Impacts of dreissenid mussels (Dreissena spp.) on Great Lakes ecosystems are well documented, and a better understanding of mechanisms that cause variation in mussel abundance is needed. An outstanding question is how much mussel biomass is consumed by fish predation. A significant difficulty for investigating mussel consumption by fish is that mussels in stomachs are often a mix of crushed shell and flesh. Here, we provide information on the relationship between shell-and-flesh dry weight measurements and flesh-only dry weight of two species of dreissenid mussel, quagga (Dreissena rostiformis bugensis) and zebra (Dreissena polymorpha), to be used in formulating conservative estimates of flesh-only dry weight in fish diets. Dry weight analyses were conducted to simulate stomach contents ranging from small (individual mussels) to large (aggregate of mussels). All measurements were taken at the USGS Lake Erie Biological Station in Sandusky, Ohio using quagga and zebra mussels collected from Lake Erie in May, 2014.