Geology topics

Ryan J. Heise

Publications and source records attributed to Ryan J. Heise.

4 recordsLinked to original sources

USGS2018

Food web contaminant dynamics of a large Atlantic Slope river: Implications for common and imperiled species

Persistent and bioaccumulative contaminants often reach concentrations that threaten aquatic life by causing alterations in organism behavior and development, disruption of biological processes, reproductive abnormalities, and mortality. The objectives of this research were to determine the aquatic food web structure and trophic transfer and accumulation of contaminants within a riverine ecosystem and identify potential stressors to the health of an imperiled fish, the robust redhorse (Moxostoma robustum) and other species of conservation concern in a large Atlantic Slope (USA) river. Trophic position was determined for food web taxa by stable isotope analyses of representative producers, consumers, and organic matter of the Yadkin-Pee Dee River of North Carolina and South Carolina. Contaminant analyses were performed on water, sediment, organic matter, and aquatic biota to assess the prevalence and accumulation of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), current use pesticides (CUPs), polycyclic aromatic hydrocarbons (PAHs), and selected metals. Contaminants were prevalent in the environment and food web components of the river. PCBs were detected in 32% of biotic samples (mean 0.24 μg/g dry weight [DW], range 0.01–3.33 μg/g DW), and DDTs (legacy OCPs and metabolites) were detected in 90% (mean 0.014 μg/g DW, range 0.0004–0.29 μg/g DW). The trace metals manganese and cadmium exceeded published threshold effect concentrations in sediment (460 and 0.99 μg/g DW, respectively). Mercury was detected in all food web samples exhibiting a mean of 0.61 μg/g DW and range 0.006–2.35 μg/g DW (mean 0.13 μg/g wet weight [WW], range 0.001–0.6 μg/g WW). Concentrations exceeded the 0.2 μg/g WW aquatic life criterion for mercury in 38% of fish samples. Fish trophic magnification factors (TMFs; range 0.33–3.75) indicated that contaminant accumulation occurred from both water and dietary sources. The combination of analytical approaches applied here provides new insight into contaminant dynamics with conservation implications.

Science of the Total Environment↗

USGS2017

Declining occurrence and low colonization probability in freshwater mussel assemblages: A dynamic occurrence modeling approach

Mussel monitoring data are abundant, but methods for analyzing long-term trends in these data are often uninformative or have low power to detect changes. We used a dynamic occurrence model, which accounted for imperfect species detection in surveys, to assess changes in species occurrence in a longterm data set (1986–2011) for the Tar River basin of North Carolina, USA. Occurrence of all species decreased steadily over the time period studied. Occurrence in 1986 ranged from 0.19 for Utterbackia imbecillis to 0.60 for Fusconaia masoni . Occurrence in 2010–2011 ranged from 0.10 for Lampsilis radiata to 0.40 for F. masoni . The maximum difference between occurrence in 1986 and 2011 was a decline of 0.30 for Alasmidonta undulata . Mean persistence for all species was high (0.97, 95% CI ¼ 0.95–0.99); however, mean colonization probability was very low (,0.01, 95% CI ¼ ,0.01–0.01). These results indicate that mussels persisted at sites already occupied but that they have not colonized sites where they had not occurred previously. Our findings highlight the importance of modeling approaches that incorporate imperfect detection in estimating species occurrence and revealing temporal trends to inform conservation planning.

North Carolina↗

USGS2016

Species traits and catchment-scale habitat factors influence the occurrence of freshwater mussel populations and assemblages

Conservation of freshwater unionid mussels presents unique challenges due to their distinctive life cycle, cryptic occurrence and imperilled status. Relevant ecological information is urgently needed to guide their management and conservation. We adopted a modelling approach, which is a novel application to freshwater mussels to enhance inference on rare species, by borrowing data among species in a hierarchical framework to conduct the most comprehensive occurrence analysis for freshwater mussels to date. We incorporated imperfect detection to more accurately examine effects of biotic and abiotic factors at multiple scales on the occurrence of 14 mussel species and the entire assemblage of the Tar River Basin of North Carolina, U.S.A. The single assemblage estimate of detection probability for all species was 0.42 (95% CI, 0.36–0.47) with no species- or site-specific detection effects identified. We empirically observed 15 mussel species in the basin but estimated total species richness at 21 (95% CI, 16–24) when accounting for imperfect detection. Mean occurrence probability among species ranged from 0.04 (95% CI, 0.01–0.16) for Alasmidonta undulata, an undescribed Lampsilis sp. , and Strophitus undulatus to 0.67 (95% CI, 0.42–0.86) for Elliptio icterina . Median occurrence probability among sites was <0.30 for all species with the exception of E. icterina . Site occurrence probability generally related to mussel conservation status, with reduced occurrence for endangered and threatened species. Catchment-scale abiotic variables (stream power, agricultural land use) and species traits (brood time, host specificity, tribe) influenced the occurrence of mussel assemblages more than reach- or microhabitat-scale features. Our findings reflect the complexity of mussel ecology and indicate that habitat restoration alone may not be adequate for mussel conservation. Catchment-scale management can benefit an entire assemblage, but species-specific strategies may be necessary for successful conservation. The hierarchical multispecies modelling approach revealed findings that could not be elucidated by other means, and the approach may be applied more broadly to other river basins and regions. Accurate measures of assemblage dynamics, such as occurrence and species richness, are required to create management plans for effective conservation.

Freshwater Biology↗

USGS2013

Short-term effects of small dam removal on freshwater mussel assemblage

Dam removal is increasingly used to restore lotic habitat and biota, but its effects on freshwater mussels (family Unionidae) are not well known. We conducted a four-year study to assess short-term effects on mussels after removal of a small hydropower dam on the Deep River (Cape Fear River drainage), North Carolina, USA, in 2006. We conducted annual pre- and post-removal monitoring of mussel density, richness, and survival (post removal only) with transect surveys and quadrat excavation, and assessed changes in substrate composition at two impact sites (tailrace and impoundment) and two reference sites. Before-after-control-impact (BACI) analyses of variance did not detect a significant change in mussel density (total or individually for the three most abundant species), species richness, Eastern Elliptio ( Elliptio complanata ) mean length, or substrate composition in the tailrace or drained impoundment following dam removal. Apparent annual survival estimates of Eastern Elliptio at the tailrace site did not differ among sampling periods and were similar to control sites. We observed minimal mussel mortality from stranding in the dewatered reservoir. These results demonstrate that adverse short-term impacts of dam removal on downstream mussel assemblages can be minimized with appropriate planning, timing, and removal techniques, but additional monitoring is warranted to determine long-term effects on mussels within the restored river reach.

North Carolina↗