Geology Reports⌕ Search

Geology topics

C. Edward Proffitt

Publications and source records attributed to C. Edward Proffitt.

10 recordsLinked to original sources
USGS2023

Temperature thresholds for leaf damage from two extreme freeze events (2018 and 2021) near the northern range limit of black mangroves (Avicennia germinans) in southeastern North America

Extreme winter temperatures govern the northern range limit of black mangroves ( Avicennia germinans ) in southeastern North America. There is a pressing need for studies that advance our understanding of how extreme cold temperature events affect mangroves near their range limits. However, such events are infrequent and challenging to study at regional scales. Here, we compared the damage to mangroves from extreme freeze events in 2018 and 2021, using local data from sites in USA (Florida, Louisiana, and Texas) and northeastern Mexico (Tamaulipas). In 2018, mangrove damage was concentrated in Louisiana and the upper Texas coast, where minimum temperatures ranged from -4 °C to -7 °C. In 2021, damage from a more severe freeze event was concentrated along the central to northern coasts of Texas, where minimum temperatures ranged from -4 °C to -10 °C. We used regional temperature and vegetation data from these events to quantify temperature thresholds for A. germinans leaf damage. Our results indicate that A. germinans leaf damage is likely to occur when temperatures are between -4 °C and -6 °C. These findings help refine temperature thresholds for A. germinans leaf damage and advance understanding of the effects of extreme freeze events on mangrove range expansion. This information is valuable for anticipating future range dynamics in a warming world.

Atlantic Ocean, Gulf of Mexico↗
USGS2023

Rapidly changing range limits in a warming world: Critical data limitations and knowledge gaps for advancing understanding of mangrove range dynamics in the southeastern USA

Climate change is altering species’ range limits and transforming ecosystems. For example, warming temperatures are leading to the range expansion of tropical, cold-sensitive species at the expense of their cold-tolerant counterparts. In some temperate and subtropical coastal wetlands, warming winters are enabling mangrove forest encroachment into salt marsh, which is a major regime shift that has significant ecological and societal ramifications. Here, we synthesized existing data and expert knowledge to assess the distribution of mangroves near rapidly changing range limits in the southeastern USA. We used expert elicitation to identify data limitations and highlight knowledge gaps for advancing understanding of past, current, and future range dynamics. Mangroves near poleward range limits are often shorter, wider, and more shrublike compared to their tropical counterparts that grow as tall forests in freeze-free, resource-rich environments. The northern range limits of mangroves in the southeastern USA are particularly dynamic and climate sensitive due to abundance of suitable coastal wetland habitat and the exposure of mangroves to winter temperature extremes that are much colder than comparable range limits on other continents. Thus, there is need for methodological refinements and improved spatiotemporal data regarding changes in mangrove structure and abundance near northern range limits in the southeastern USA. Advancing understanding of rapidly changing range limits is critical for foundation plant species such as mangroves, as it provides a basis for anticipating and preparing for the cascading effects of climate-induced species redistribution on ecosystems and the human communities that depend on their ecosystem services.

Alabama, Florida, Louisiana, Mississippi, Texas↗
USGS2016

Marine ecoregion and Deepwater Horizon oil spill affect recruitment and population structure of a salt marsh snail

Marine species with planktonic larvae often have high spatial and temporal variation in recruitment that leads to subsequent variation in the ecology of benthic adults. Using a combination of published and unpublished data, we compared the population structure of the salt marsh snail, Littoraria irrorata , between the South Atlantic Bight and the Gulf Coast of the United States to infer geographic differences in recruitment and to test the hypothesis that the Deepwater Horizon oil spill led to widespread recruitment failure of L. irrorata in Louisiana in 2010. Size-frequency distributions in both ecoregions were bimodal, with troughs in the distributions consistent with a transition from sub-adults to adults at ~13 mm in shell length as reported in the literature; however, adult snails reached larger sizes in the Gulf Coast. The ratio of sub-adults to adults was 1.5–2 times greater in the South Atlantic Bight than the Gulf Coast, consistent with higher recruitment rates in the South Atlantic Bight. Higher recruitment rates in the South Atlantic Bight could contribute to higher snail densities and reduced adult growth in this region. The ratio of sub-adults to adults in Louisiana was lower in 2011 than in previous years, and began to recover in 2012–2014, consistent with widespread recruitment failure in 2010, when large expanses of spilled oil were present in coastal waters. Our results reveal an important difference in the ecology of a key salt marsh invertebrate between the two ecoregions, and also suggest that the Deepwater Horizon oil spill may have caused widespread recruitment failure in this species and perhaps others with similar planktonic larval stages.

Ecosphere↗
USGS2006

Genetic Considerations for the Restoration of Smooth Cordgrass (Spartina alterniflora) Within Its Native Range

In order to remain viable over many generations, plant populations require the ability to respond adaptively to a changing environment. Such adaptive potential is directly controlled by underlying genetic variation, which can be measured in terms of both heterozygosity at the individual level and clonal, or genotypic diversity at the population level. This report summarizes research relating to the importance of genetic diversity in the restoration of salt marsh smooth cordgrass, Spartina alterniflora, a dominant member of low elevation intertidal marshes throughout the northern Gulf of Mexico and Atlantic Coasts of North America. Recent research has indicated that S. alterniflora is a partially clonal species characterized by the recruitment of seedlings exclusively during the initial colonization phase of population establishment. A major consequence of this finding is that clonal diversity generally peaks rather early in the development of a restored marsh, depending on the rate of natural immigration and/or the clonal diversity of planting units, and then undergoes a steady decline over geological time spans because of stochastic mortality and intraspecific competition. Low levels of clonal diversity resulting from restricted immigration or clonally depauperate planting materials in turn places strict limits on opportunities for outcrossing in a species known to suffer from severe inbreeding depression. Low clonal diversity may further lead to declining levels of heterozyosity of individual clones, which directly affects competitive ability. In addition, the planting of genetically diverse plant materials should take into account the genetic and adaptive differentiation that takes place when plant populations are widely separated in space and/or dwell under varying sets of environmental conditions. Thus, steps should be taken to ensure that S. alterniflora clones developed for restorative plantings are both genetically diverse and sufficiently pre-adapted to environmental conditions at the proposed restoration site. This can be achieved by growing plant materials collected from local sources and by either taking care to maintain relatively high levels of clonal diversity or by planting clones at sufficiently low densities that they will not quickly grow to monopolize a restoration site without first producing several generations of sexual recruits through crosses with nearby native populations.

Open-File Report↗
USGS2005

Grazing by the intertidal gastropod Melampus coffeus greatly increases mangrove leaf litter degradation rates

Melampus coffeus , a pulmonate gastropod, forages for mangrove leaf litter at low tide and climbs tree trunks to avoid inundation during high tide. Unlike many grazers, these snails can assimilate mangrove leaf material. At Boca Ceiga Bay, Florida, densities of adult snails were high (>100 snails m –2 ) throughout a 130 m wide intertidal zone. A mark–recapture study indicated that over the course of 1 mo 48.6 ± 6.1% of snails returned to their initial tree during high tides, while those that did relocate moved 6.66 ± 0.60 m and were recorded from 33 new trees at high tide. A field experiment comparing tethered leaves with small and large litter bags showed that snail grazing greatly increased the rate of red ( Rhizophora mangle ) and black ( Avicennia germinans ) leaf litter breakdown. Grazing by M. coffeus resulted in 90% weight loss in <4 wk ( A. germinans ) and 7 wk ( R. mangle ), compared to slower breakdown in litter bags (12 to 26 wk, A. germinans ; >26 wk, R. mangle ). Another experiment showed greater leaf litter accumulation on the forest floor in plots where M. coffeus was excluded. The decomposition coefficient ( k ) was 10× greater when M. coffeus grazing was allowed than k for any studies that enclosed leaves in litterbags. During our experiment, M. coffeus consumed an estimated 40.5% of mangrove leaf fall, and 19.8% of leaf litter was exported as particulate or dissolved material. This M. coffeus population can produce an estimated 3 × 10 6 larvae m –2 yr –1 , which suggests that the larval pathway is an important conduit of mangrove leaf resources to the estuarine food web.

Florida↗
USGS2003

Facilitation of survival and growth of Baccharis halimifolia L. by Spartina alterniflora Loisel. In a created Louisiana salt marsh

Coastal wetland loss is a major environmental issue in the Mississippi Delta region of the southern United States, where grasses such as Spartina alterniflora may play a critical role both as early colonizers on created sites and as facilitators of other marsh grasses and shrubs, particularly at high intertidal elevations. We explored the potential role of S. alterniflora as a facilitator of the colonization and growth of the shrub Baccharis halimifolia at two created wetlands in southwestern Louisiana through a combination of plant surveys and experimentation. Surveys for the presence of B. halimifolia inside and outside the bare centers of S. alterniflora clones that had begun to senesce inwardly were conducted at a 4-yr-old site originally created in 1993. The percent of clones containing B. halimifolia and the number of individual B. halimifolia plants per clone increased with increasing S. alterniflora clone size and decreased with increasing distance from an adjacent containment berm. Two experiments conducted at a second 4-yr-old site that was originally created in 1996 were designed to assess seed capture and growth of seedlings of B. halimifolia inside S. alterniflora clones. These experiments revealed that while significantly fewer seeds settle inside clones, those seedlings that grow in such areas gain a clear advantage in terms of both survival and rate of growth, which helps to explain the results of the initial survey and testifies to the role of S. alterniflora as a nurse plant in newly-created high intertidal marshes.

Louisiana↗
USGS2001

Abstracts from "Coastal Marsh Dieback in the Northern Gulf of Mexico: Extent, Causes, Consequences, and Remedies

In the spring of 2000, scientists discovered a new and unprecedented loss of salt marsh vegetation in coastal Louisiana and other areas along the northern coast of the Gulf of Mexico. This dieback of salt marsh vegetation, sometimes called the brown marsh phenomenon', primarily involved the rapid browning and dieback of smooth cordgrass (Spanina alterniflora). Coastal Louisiana has already undergone huge, historical losses of coastal marsh due to both human-induced and natural factors, and the current overall rate of wetland loss (25-35 sq mi 65-91 SQ KM each year) stands to threaten Louisiana's coastal ecosystem, infrastructure, and economy. On January 11-12, 2001, individuals from Federal and State agencies, universities, and the private sector met at the conference 'Coastal Marsh Dieback in the Northern Gulf of Mexico: Extent, Causes, Consequences, and Remedies' to discuss and share information shout the marsh dieback. Presentations discussed trends in the progress of dieback during the summer of 2000 and in environmental conditions occurring at field study sites, possible causes including drought and Mississippi low flow' conditions, changes in soil conditions (salinity, the bioavailability of metals, pathogens, etc.), the potential for wetland loss that could occur if above and below normality occurs and is sustained over an extended period, advanced techniques for tracking the dieback via aerial photography and remote sensing, linkages of marsh hydrology to the dieback, and mechanisms of modeling dieback and recovery. In addition, presentations were made regarding development of a web site to facilitate information sharing and progress in preparation for requests for proposals based on an emergency appropriation by the U.S. Congress. All findings tended to support the idea that the dieback constituted a continuing environmental emergency and research and natural resource management efforts should be expended accordingly.

Information and Technology Report↗
USGS1999

Response

No abstract available.

Ecological Applications↗