Runnels, a climate adaptation technique that drains surface water to restore marsh vegetation and... more Runnels, a climate adaptation technique that drains surface water to restore marsh vegetation and habitat, are increasingly being used to prevent the formation of shallow water impoundments or pannes in salt marshes that result in the loss of important ecosystem services. However, we know little about the effect of runnels on salt marsh biogeochemistry. This study measured how sediment characteristics and rates of nitrogen cycle processes were altered by impounded water and vegetation loss, and whether runnels can restore these marsh attributes to reference conditions. Impounded areas were 52 ± 4% less vegetated than nearby intact marsh, with 11 ± 2% less organic matter and 24 ± 5% higher bulk density. Additionally, impoundments removed 32 ± 32 µmol N m−2 d−1 less than reference marsh areas via denitrification. At six of the 11 runneled sites, vegetation percent cover increased by 40 ± 5%, accompanied by a 7 ± 3% recovery of organic matter and a 9 ± 6% reduction of bulk density. At ...
Impacts the Growth and Survival of Red Drum (Sciaenops ocellatus)"). Neither has been externally ... more Impacts the Growth and Survival of Red Drum (Sciaenops ocellatus)"). Neither has been externally peer reviewed and both are published as submitted by the authors. Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Impacts the Growth and Survival of Red Drum (Sciaenops ocellatus)") and a reply (Response to: Conway et al. (2023), Red Drum Salinity Tolerance: Comments on Ackerly et al. "Short-Term Salinity Stress During Early Development Communicated by Linda Deegan.
Population Size and Site Fidelity of Fundulus heteroclitus in a Macrotidal Saltmarsh Creek
The Biological Bulletin, Oct 1, 1998
Fundulus heteroclitus (mummichog) is the numerically dominant fish species found in salt marshes ... more Fundulus heteroclitus (mummichog) is the numerically dominant fish species found in salt marshes from Florida to Nova Scotia. These areas exhibit a wide range of fluctuation in environmental conditions such as temperature, salinity, and tidal range. Mummichogs are known to be ...
A critical challenge to understanding the response of ecosystems to anthropogenic drivers is char... more A critical challenge to understanding the response of ecosystems to anthropogenic drivers is characterizing the spatial and temporal variability of controls on food web dynamics. We used a long-term (9 yr) isotope survey and a community metric isotope approach to determine the major physical factors influencing the source of energy to estuarine food webs. Overall, food web architecture was similar throughout the estuary, but there were some spatial differences. We observed greater overall variability in the primary production source to the food web in the upper estuary (which is more influenced by freshwater inputs) compared with the middle and lower estuary. The trophic level of one dominant species, mummichog Fundulus heteroclitus, was also highly correlated with tidal height, which controls high marsh access in the middle estuary. We also observed a strong influence of freshwater input on the benthic-pelagic coupling in the upper estuary. Our work demonstrates that the temporal and spatial variability of food webs in estuarine systems is highly coupled to physical drivers.
Hydrologic and Biological Controls on the Fate of Watershed-derived Nitrogen in Estuaries: Insights from "Whole-estuary" Stable Isotope Enrichments
AGUSM, May 1, 2005
In situ nitrogen isotope tracer additions are becoming an increasingly widespread tool for unders... more In situ nitrogen isotope tracer additions are becoming an increasingly widespread tool for understanding nitrogen fate and turnover in stream ecosystems. The approach however has only been attempted twice in estuaries. Isotope enrichment of these systems represents a several-fold increase in scale, and added challenges of bidirectional flow. Despite these potential limitations, the approach has yielded insights into nitrogen uptake, trophic transfer, and recycling on the scale of tens to hundreds of thousands of cubic meters of water and up to 4 kilometers of benthic area. The large-scale use of 15N tracer additions to estuaries has provided the unique ability to quantify multiple nitrogen (N) flow pathways under natural hydrologic and geochemical conditions. Estuarine 15N enrichment studies have been performed in two estuaries in the Plum Island LTER (Parker and Rowley Rivers) that differed in geomorphology, hydrology and biological structure. In each experiment 15N-nitrate tracer was added at the head of the estuaries in order to label watershed N entering the estuary and provided a "tag" for that N as it was processed in the estuary. 15N tracer released into the long water residence time Parker River was processed primarily (approx. 100 percent) through phytoplankton which subsequently supported high rates of secondary production in both the water column and benthos. In contrast, tracer released into the short water residence time Rowley River was primarily (75-80 percent of added 15N) advected, unaltered out of the estuary as nitrate. The 15N sinks that did exist within the Rowley were divided evenly between assimilation by benthic autotrophs (including uptake by marsh macrophytes) and denitrification. Recycling of the assimilated 15N back into the water column was a more important mechanism of N transfer than support of secondary production in the Rowley. Collectively, the use of large-scale stable 15N isotope additions in these contrasting estuaries has allowed us to examine how geomorphology, hydrology, and biotic structure interact to regulate estuarine N processing.
Nitrogen dynamics and foodweb interactions in two contrasting Arctic streams
AGU Spring Meeting Abstracts, May 1, 2005
We used a 15N tracer addition to quantify nitrogen dynamics and foodweb interactions in two contr... more We used a 15N tracer addition to quantify nitrogen dynamics and foodweb interactions in two contrasting tributaries of the Ivishak River in the Arctic National Wildlife Refuge, Alaska. We added 15NH4Cl simultaneously to spring and mountain streams for 4 weeks in summer of 2002 and measured 15N: 14N ratios in inorganic and biomass compartments over distance and time. 15N labeling was rapid in both streams despite low temperatures and higher than expected discharge. Compartment-specific ammonium uptake lengths (Sw) in the flashy mountain stream were initially high (7 km) due to elevated discharge, but decreased significantly thereafter (200-400 m). Uptake lengths in the hydrologically stable spring stream were similar throughout the release, but varied slightly between compartments (80-150 m). Most of the added 15N-NH4 in the spring stream was taken up by bryophytes, whereas active uptake of N in the mountain stream was by filamentous algae. Chironomids (Diamesinae and Orthocladiinae) appeared to be feeding primarily on epilithon and filamentous algae, whereas simuliids were feeding on seston in both streams. Our data show that nitrogen retention in the two streams differed and depended on turnover of organism biomass, which was controlled by physical conditions such as temperature and discharge variability.
Long-term records of the flow of water through tidal channels are essential to constrain the budg... more Long-term records of the flow of water through tidal channels are essential to constrain the budgets of sediments and biogeochemical compounds in salt marshes. Statistical models which relate discharge to water level allow the estimation of such records from more easily obtained records of water stage in the channel. Here we compare four different types of stage-discharge models, each of which captures different characteristics of the stage-discharge relationship. We estimate and validate each of these models on a two-month long time series of stage and discharge obtained with an Acoustic Doppler Current Profiler in a salt marsh channel. We find that the best performance is obtained by models that account for the nonlinear and time-varying nature of the stage-discharge relationship. Good performance can also be obtained from a simplified version of these models, which captures nonlinearity and nonstationarity without the complexity of the fully nonlinear or time-varying models.
Canadian Journal of Fisheries and Aquatic Sciences, Oct 1, 2004
In many long-lived species such as Arctic grayling (Thymallus arcticus), population growth rate i... more In many long-lived species such as Arctic grayling (Thymallus arcticus), population growth rate is most sensitive to changes in adult survival probabilities. Understanding the factors that regulate adult survival in this species should provide insight into the population dynamics of this and other long-lived Arctic species. Using the program MARK, we analyzed 17 years of mark-recapture data to estimate survival rates for Arctic grayling in the Kuparuk River, Alaska, from 1985 to 2000. Mean annual survival rates overall ranged from 0.39 to 1.0 and averaged 0.71 ± 0.05 for resident and 0.75 ± 0.05 for nonresident fish. Spending the summer in the more productive fertilized zone of the experimental reach had no influence on survival despite higher productivity on all trophic levels and consistently higher growth rates in Arctic grayling. None of the environmental (stream temperature, discharge, winter severity, and incidence of drought) or population parameters (growth, condition factor, and mean fish size) that we examined explained significant amounts of variance in survival rates. The lack of responsiveness of survival to annual environmental conditions was unexpected and suggests that multiyear factors or life history tactics that maintain survival at the expense of growth and fecundity likely determine survival. Résumé : Chez plusieurs espèces à forte longévité, telles que l'ombre arctique (Thymalus arcticus), le taux de croissance de la population est particulièrement sensible aux changements de probabilité de survie des adultes. La compréhension des facteurs qui contrôlent la survie des adultes chez cette espèce devrait fournir des perspectives sur la dynamique de population de cette espèce et d'autres espèces arctiques qui vivent longtemps. À l'aide du logiciel MARK, nous avons analysé des données de marquage-recapture étalées sur 17 années afin d'estimer les taux de survie des ombres arctiques de la rivière Kurapuk de 1985 à 2000. Les taux moyens annuels de survie varient dans l'ensemble de 0,39 à 1,0; ils sont en moyenne de 0,71 ± 0,05 pour les poissons résidants et de 0,75 ± 0,05 pour les non résidants. Le passage de l'été dans la section enrichie et plus productive de la zone expérimentale n'influence pas la survie, malgré une productivité accrue de tous les niveaux trophiques et des taux de croissance uniformément plus élevés chez l'ombre arctique. Aucune des variables examinées de l'environnement (température du cours d'eau, débit, rigueur de l'hiver, présence de sécheresses) ou de la population (croissance, coefficient de condition, taille moyenne des poissons) n'explique de partie significative de la variance des taux de survie. Ce manque de réaction de la survie aux conditions annuelles du milieu est inattendu et il laisse croire que la survie est déterminée par des variables ou des tactiques démographiques qui agissent sur plusieurs années pour maintenir la survie aux dépens de la croissance et de la fécondité.
Inter-annual fidelity to summer feeding sites was assessed in adult Arctic grayling, Thymallus ar... more Inter-annual fidelity to summer feeding sites was assessed in adult Arctic grayling, Thymallus arcticus, in the Kuparuk River, Alaska using long-term (15 years) records of individually tagged fish. The Kuparuk River has been the site of a long-term fertilization experiment which allowed us to evaluate the effects of habitat quality on site fidelity. Fidelity to the entire 5 km experimental reach, the reference or fertilized zone of the river and to specific river locations was examined. On average, 32% of the arctic grayling caught in the experimental reach were recaptured within the reach in subsequent years. Grayling that returned to the reach displayed strong fidelity to river zones as well as to specific sites on the river. More than half of the fish were recaptured within 300 meters of the site where they were captured in previous years. There was no significant difference in fidelity to either the reference or the more productive fertilized zone. Unexpectedly, fidelity was unrelated to fish size (29-43 cm TL) or previous summer's growth. Strong site fidelity appears to be an adaptation to a short summer during which sufficient resources must be acquired to sustain the fish through the long (9 month) Arctic winter leaving little time to explore alternative locations.
The response of fishes to submerged aquatic vegetation complexity in two ecoregions of the mid-Atlantic bight: Buzzards Bay and Chesapeake Bay
Estuaries, Feb 1, 2002
... JASON C. WYDA, LINDA A. DEEGAN*, JEFFREY E. HUGHES, AND MELISSA J. WEAVER ... Excess water w... more ... JASON C. WYDA, LINDA A. DEEGAN*, JEFFREY E. HUGHES, AND MELISSA J. WEAVER ... Excess water was re-moved using a salad spinner and the above-sedi-ment vegetation, including epiphytes, was weighed (wet weight, 0.1 g). At each site divers counted the number of ...
Falmouth Rod & Gun Club Sporting Safety Conservation and Education Fund of Falmouth (SSCEFF) Falm... more Falmouth Rod & Gun Club Sporting Safety Conservation and Education Fund of Falmouth (SSCEFF) Falmouth DNR The many fish sponsors: >100 individuals and organizations adopted ~1000 herring ~175 students from Falmouth public schools About 85% of the program costs in 2015 and a similar percentage in 2016
A prominent form of salt marsh loss is interior conversion to open water, driven by sea level ris... more A prominent form of salt marsh loss is interior conversion to open water, driven by sea level rise in interaction with human activity and other stressors. Persistent inundation drowns vegetation and contributes to open water conversion in salt marsh interiors. Runnels are shallow channels originally developed in Australia to control mosquitoes by draining standing water, but recently used to restore marsh vegetation in the USA. Documentation on runnel efficacy is not widely available; yet over the past 10 years dozens of coastal adaptation projects in the northeastern USA have incorporated runnels. To better understand the efficacy of runnels used for restoration, we organized a workshop of 70 experts and stakeholders in coastal resource management. Through the workshop we developed a collective understanding of how runnels might be used to slow or reverse open water conversion, and identified unresolved questions. In this paper we present a synthesis of workshop discussions and results from a promising case study in which vegetation was restored at a degraded marsh within a few years of runnel construction. Despite case study outcomes, key questions remain on long-term runnel efficacy in marshes differing in elevation, tidal range, and management history. Runnel construction is unlikely to improve long-term marsh resilience alone, as it cannot address underlying causes of open water conversion. As a part of holistic climate planning that includes other management interventions, runnels may "buy time" for salt marshes to respond to management action, or adapt to sea level rise.
Numerous investigations have demonstrated relationships between fisheries yields and the high pri... more Numerous investigations have demonstrated relationships between fisheries yields and the high primary productivities typical of estuaries and estuarine plume ecosystems. Along with the loss of wetlands, presumably so go functions related to them such as commercial harvests of fisheries. However, perhaps the most perplexing aspect of the Mississippi River delta ecosystem is the fact that there is little indication that fisheries productivity has decreased. Why aren't landings decreasing? We favor the explanation that fisheries of today reflect a degraded ecosystem attributable to environmental damages that began in the 1920s or earlier but that accelerated during the twentieth century. There are a few thorough reviews of differential use of habitat by estuarine fishes from other deltaic ecosystems that may allow us to speculate about how the loss of habitat in Louisiana may impact fisheries production. Greater than 75 % of the species that support fisheries in Louisiana are considered to be estuarine-resident or -dependent, and therefore it is likely to end badly for the Sportsman's Paradise if large-scale restoration is not possible, or if possible, not undertaken. Large-scale restoration will cause shifts in the locations of the major fisheries but it may be the only hope of maintaining sustainable fisheries.
Restoring coastal marshes requires managing nutrient loads but it is not clear how quickly carbon... more Restoring coastal marshes requires managing nutrient loads but it is not clear how quickly carbon cycling can rebound. • In a long-term experiment, ceasing enrichment returned rates of ecosystem respiration to reference levels within one year. • The soil stabilization processes that affect decomposition likewise immediately reverted to reference levels. • Curbing coastal nutrient enrichment could rapidly improve carbon sequestration in the short-term and increase coastal resilience in the long-term.
Consumer-mediated movement can couple food webs in distinct habitats and facilitate energy flow b... more Consumer-mediated movement can couple food webs in distinct habitats and facilitate energy flow between them. In New England saltmarshes, mummichog (Fundulus heteroclitus) use the flooding spring tides to access the high marsh platform and eat invertebrate prey, coupling the high marsh and aquatic creek food webs by gathering energy produced on the high marsh and making it available to the aquatic food web. Changes in the geomorphology of saltmarsh creek edges greatly influence the survival, biomass, and resource use of mummichog populations. Here, we use gut content analysis and field surveys to quantify the effect of altered creek edge geomorphology of mummichog predation on terrestrial invertebrate prey found on the high marsh surface. Fish populations in creeks with greater connectivity had a higher total biomass of terrestrial invertebrates in their guts. However, bomb calorimetry showed no difference in the average caloric content of mummichog individuals from creeks with different creek edge geomorphology. Additionally, we did not observe differences between the biomass and length distributions of mummichog in those creeks. While altered creek edge geomorphology has no effect the condition of the individual mummichog, it does decrease the total number of mummichog supported by a marsh creek and therefore decreases the total amount of high marsh production fluxed by mummichog to the aquatic habitat, decreasing coupling between the terrestrial and aquatic food webs.
The Effect of Mississippi River Delta Lobe Development on the Habitat Composition and Diversity of Louisiana Coastal Wetlands
American Midland Naturalist, Oct 1, 1986
... Large increases in area in lobes over approximately 500,000 ha lead to only small changes in ... more ... Large increases in area in lobes over approximately 500,000 ha lead to only small changes in habitat number. Shannon-Wiener habitat diversity peaks in the La-fourche Delta Lobe (Table 1). ... In. ML Broussard (ed.). Deltas, models for ex-ploration. Houston Geological Society. ...
Uploads
Papers by Linda Deegan