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A significant and recruiting population of Obovaria olivaria (Hickorynut Mussel) was confirmed in the Mississagi River, Lake Huron drainage, ON, Canada. This large river unionid mussel is known to use Acipenser fulvescens (Lake Sturgeon) and Scaphirhynchus platorynchus (Shovelnose Sturgeon) as hosts. The Mississagi River is known to have a spawning Lake Sturgeon population. In 9.1 person-hours of snorkel and SCUBA searches, 10 live O. olivaria ranging in length from 36 to 79 mm, including six gravid females, were collected in sandy substrates with water depths from 1.5 to 4 m. Obovaria olivaria in the Mississagi River represent a significant range disjunction from the other extant populations in Canada in the Ottawa and St. Lawrence river drainages. As the conservation status of this rare mussel in Canada is assessed, the geographic genetic population structure and spatial extent among known areas should be studied to understand the post-glacial redistribution of the species.
The relationships between stream flow regime and macroinvertebrate diversity, community structure, and functional feeding groups (FFG) were examined to determine if the biodiversity and macroinvertebrate fauna of non-perennial streams are significantly different from those of perennial streams. The study was conducted in northeastern Massachusetts at headwater stream sites of varying flow permanence (perennial, intermittent, and ephemeral). ANOVA confirmed no significant difference in Shannon-Wiener diversity (H′) between stream types, demonstrating that non-perennial streams maintain diverse and even macroinvertebrate communities. Whereas taxa richness was equal among intermittent and perennial sites, ephemeral richness was lower due to their significantly lower riffle richness. Qualitatively, two non-perennial sites were higher in grand total H′ diversity and taxa richness than perennial sites. Community structure was also related to flow regime, as hierarchical cluster analysis (HCA) based on taxa presence produced three distinct groups consistent with stream type, and FFG analysis provided further evidence of distinct communities, with a transition in FFGs from perennial to ephemeral sites. This study concludes that non-perennial streams are biologically diverse and maintain distinct benthic communities and therefore contribute to stream biodiversity and river ecosystems.
Deciduous leaf litter is often a primary source of energy at the base of the food web in seasonal woodland ponds (e.g., vernal or autumnal pools), which are common in the northeastern United States. It is therefore important to understand how leaf diet affects growth of detritivores, such as the caddisfly Limnephilus indivisus Walker, that feed almost exclusively on submerged plant matter in seasonal pond systems. Growth may relate to how rapidly a caddisfly is able to complete its larval development and pupate, and hence its ability to survive in small ponds with short hydroperiods. Growth is also related to the maximum size the larva achieves. In many organisms, attaining a larger size conveys several distinct advantages: larger individuals typically have higher survival rates and increased fecundity, and hence greater fitness compared to smaller conspecifics or competing sympatric species. To assess how leaf diet influences the growth of larvae of L. indivisus, we conducted a controlled experiment to test how different leaf diets influenced larval growth. The leaf diet experiment was set up as follows: Treatment 1: Acer rubrum (Red Maple), Treatment 2: Quercus spp. (oak), and Treatment 3: Red Maple and oak. L. indivisus that were fed oak leaves or a mix of oak and Red Maple leaves grew significantly larger than larvae fed Red Maple leaves only. In Treatment 3, the caddisfly was observed more frequently on the oak leaf compared to the Red Maple leaf. Although L. indivisus selected oak leaves more often during the experiment, oak leaves were less abundant than maple leaves at our study site. We hypothesize that the oak leaves provide more nutrients to L. indivisus due to a combination of physical, biological, and chemical properties which results in more larval growth.
The Saco River estuary is a narrow estuary in southern Maine, for which the fauna has not been described in nearly 30 years. Beach seining, otter trawling, and beam trawling were conducted between April and October of 2007 and 2008 to assess seasonal variation in fish assemblage structure. Twenty-four species were observed over the two sampling seasons, and nearly all species were at lengths indicative of juvenile age. Clupea harengus (Atlantic Herring), Pseudopleuronectes americanus (Winter Flounder), Anguilla rostrata (American Eel), Microgadus tomcod (Atlantic Tomcod), Pomatomus saltatrix (Bluefish), and Osmerus mordax (Rainbow Smelt) are either commercially or recreationally valuable, while Acipenser oxyrynchus oxyrynchus (Atlantic Sturgeon), Alosa aestivalis (Blueback Herring), and Rainbow Smelt are federally listed species of concern. Substantial historical assemblage changes were observed, including both the loss of commercially important species and the addition of species of concern. Regular monitoring of estuarine habitats is necessary to identify changes in assemblages and to better understand potential drivers of ecosystem change.
Movements of juvenile Homarus americanus (American Lobster; hereafter lobster) on and around a naturally occurring rock reef were monitored over a 3-year period. Lobsters were sampled with baited traps deployed at each often sites. Catch-per-unit-effort (CPUE) and number of lobsters collected per trap haul was calculated for each sampling event. Physical habitat, visually characterized by underwater video and diver observations, differed among sites. Lobster CPUE was significantly greater at rocky sites (>70% density of cobble and/or boulder) containing complex structure, vertical relief from the seafloor, and colonies of macroalgae, sponge, and hydroids. Lobster CPUE was highest from late June to mid-July. Lobsters ranged from 18 to 82 mm carapace length (CL), with 90.7% of tagged lobsters measuring between 30 to 60 mm CL. Relative lobster abundance remained similar over the course of the study. Catch data were kriged to illustrate spatial patterns of distribution. Over the study period, a total of 934 lobsters were tagged and 66 were recaptured, for an overall recapture rate of 7.1%. The majority of recaptured animals (88%) were found at the original tagging site or adjacent sites, with one lobster remaining at liberty for 397 days. Most juvenile lobsters showed fidelity to their initial site of capture on a small, relatively isolated patch of rock-reef habitat in the central basin of Long Island Sound.
East Foundry Cove and Constitution Marsh are located on the east side of the Hudson River, 85 km upriver from lower Manhattan. Between 1965 and 1971, Marathon Battery Company discharged an estimated 51,004 kg of particulate cadmium, and 1569 kg of soluble cadmium were discharged directly into East Foundry Cove, which became a Superfund site in 1994. Dredging and restoration of East Foundry Cove were completed in 1996. Cadmium concentrations were reduced from greater than 900 mg/kg to less than 3 mg/kg in East Foundry Cove. Constitution Marsh and South Cove were not included in Superfund restoration. For this study, 738 surface sediment samples were collected from 15 sampling sites on 8 occasions from 18 September 1997 to 30 October 1998. Diatoms were identified and enumerated for each collected sample. These data were analyzed using Bray-Curtis similarity, MDS ordination, analysis of similarity (ANOSIM), and similarity of percentages (SIMPER). Cadmium concentrations (mg/kg) were also determined for each sample. Results show the communities of diatoms were different in two stations (1 and 3) in East Foundry Cove from the remainder of the stations in the study. However, one East Foundry Cove station (2) was more similar to the stations in South Cove and the southern stations of Constitution Marsh. Three of the most abundant taxa, Navicula gregaria, Cyclotella meneghiniana, and Cocconeis placentula var. lineata, were present in similar proportions at all sampling sites. Navicula gregaria, however, occurred in greater relative abundance at stations 4 and 5 and in Constitution Marsh, adjacent to restored East Foundry Cove, than in any other stations.
Productivity is a primary parameter used in waterfowl population models; however, few long-term metrics of reproductive output exist for eastern North American waterfowl. We used 52 years of brood survey data from throughout Maine to determine mean Class III brood sizes for Lophodytes cucullatus (Hooded Merganser), Anas platyrhynchos (Mallard), Anas rubripes (American Black Duck), Aix sponsa (Wood Duck), Aythya collaris (Ring-necked Duck), and Bucephala clangula (Common Goldeneye). Using model selection with theoretic-information approaches, we also investigated effects of wetland type, mean ambient temperature during nesting and brood rearing, and year (1955–2007) on trends in brood sizes. Brood sizes declined throughout the survey period for American Black Ducks (-0.88 ducklings/brood), Wood Ducks (-0.91), Ring-necked Ducks (-1.75), and Common Goldeneyes (-1.45). Declines in brood sizes in Maine are consistent with that of other metrics of productivity (e.g., age ratios of harvested waterfowl) for breeding ducks in Maine and may be cause for concern, especially given that declines in brood sizes were observed across a range of species with highly disparate life-history strategies. Declines in age ratios of hunter-harvested ducks could be indicative of range-wide declines in productivity resulting from decreased breeding propensity, nest success, clutch size, or duckling survival. Our findings may suggest that declines in productivity observed in age ratios of hunter-harvested ducks are, at least in part, related to conditions during the breeding season. Thus, understanding factors influencing productivity on breeding grounds are of primary concern for long-term conservation of breeding waterfowl populations in Maine.
Haliaeetus leucocephalus (Bald Eagle) is an adaptable predatory bird that commonly captures live prey, but regularly scavenges. Large mammalian prey (e.g., Odocoileus virginianus [White-tailed Deer]) have been observed in Bald Eagle diets, but were considered scavenged. To our knowledge, Bald Eagle predation of a live ungulate has only been reported once, and occurred in Menominee County, MI. In June 2009, we captured and radiocollared a female White-tailed Deer fawn (2.7 kg) in the south-central Upper Peninsula of Michigan. The fawn was last radiolocated alive 8 h after release in a short-height (20–30 cm) grassland field along a river approximately 570 m from an eagle nest. Estimated time of mortality of the fawn was 10 h post release. Approximately 27 h post release, 2 legs, >50% fawn hide, and the radiocollar were present in the nest along with 2 eagle nestlings (estimated age 9–10 wks). We believe this was a possible predation event based on the 8-h period between fawn relocations, fawn movement, foraging behavior of the nesting eagles, and presence of the carcass remains and radiocollar in the nest.
Currently there is little known about day-roosts used by Myotis leibii (Eastern Small-footed Myotis) in the Central Appalachians. To provide insights on this species' day-roosting habits, we successfully radiotracked 5 lactating females and 5 non-reproductive males to 57 day-roosts during June and July 2008. Eastern Small-footed Myotis used ground-level rock roosts in talus slopes and rock fields (n = 53), and roosts in vertical cliff faces (n = 4). Ground-level roosts had low canopy cover (males: = 14.1 ± 2.1 [SE] %, females: = 19.6 ± 3.1%), but were located close to vegetation (males: = 3.6 ± 0.4 m, females: = 4.8 ± 0.8 m). Males switched roosts every 1.1 ± 0.04 days, traveled 41.2 ± 7.8 m between consecutive roosts, and roosted 415 ± 49.0 m from capture locations. Females switched roosts every 1.1 ± 0.06 days, traveled 66.5 ± 14.6 m between consecutive roosts, and roosted 368 ± 24.0 m from capture locations. Ground-level roosts used by females were closer to ephemeral water sources ( = 226 ± 31.2 m, n = 25) than those used by males ( = 458 ± 16.7 m, n = 28; W = 401, P < 0.01). These data illustrate the importance of rock habitat with high solar exposure near protective cover and water in day-roost selection by Eastern Small-footed Myotis.
The spatial patterns in the seed bank were examined within a coastal sanddune system. Soil samples were collected from vegetated and bare plots in three zones, each dominated by different plant species. The total number of seeds and species diversity in the seed bank were low. There were no significant patterns in total seed number. However, there were significant differences in species composition. Seeds of Artemisia campestris (Tall Wormwood) were more abundant in vegetated plots and were found in all zones, although adults are more spatially restricted. Fruits of Cyperus grayii (Gray's Sedge) were most common where adults are found. Dominant species from the site were absent from the seed bank. Overall, composition of the seed bank does not reflect composition of the adult community.
Field surveys were conducted during 1998, 2000, 2003, and 2004 within the Mingo National Wildlife Refuge in southeastern Missouri to determine if ambient ground-level ozone was impacting ozone-sensitive refuge vegetation. Ozone-induced leaf symptoms (stipple) were observed within the refuge during each survey year. Percentage of bioindicator plants exhibiting stipple were wild grape (16.1%) > Common Milkweed (16.0%) > ash (7.5%) > Black Cherry (6.7%) > Flowering Dogwood (4.9%) > Sassafras (2.3%) > Sweetgum (1.2%). By year, the incidence of symptomatic plants were 1998 (22.8%) > 2003 (3.9%) > 2000 (3.4%) > 2004 (2.5%). Cumulative ambient ozone levels (SUM60, ppb.hrs) monitored at the closest EPA monitor (Bonne Terre, MO) at time of survey were 1998 (44,886) > 2000 (39,611) > 2003 (38,465) > 2004 (15,147). The cumulative SUM60 threshold value of ozone needed to cause foliar symptoms on ozone-sensitive plants within the refuge appears to be ca. 10,000 ppb.hrs. Ozone injury is likely to occur on ozone-sensitive plant species within the refuge during most years.