An evaluation of the effects of blue crab (Callinectes sapidus) behavior on the efficacy of crab pots as a tool for estimating population abundance

Crab traps have been used extensively in studies on the population dynamics of blue crabs to provide estimates of catch per unit of effort; however, these estimates have been determined without adequate consideration of escape rates. We examined the ability of the blue crab (Callinectes sapidus) to escape crab pots and the possibility that intraspecific crab interactions have an effect on catch rates. Approximately 85% of crabs that entered a pot escaped, and 83% of crabs escaped from the bait chamber (kitchen). Blue crabs exhibited few aggressive behavioral interactions in and around the crab pot and were documented to move freely in and out of the pot. Both the mean number and size of crabs caught were significantly smaller at deeper depths. Results from this study show that current estimates of catch per unit of effort may be biased given the high escape rate of blue crabs documented in this study. The results of this paper provide a mechanistic view of trap efficacy, and reveal crab behavior in and around commercial crab pots

The Effects of Hypoxia on Macrobenthic Production and Function in the lower Rappahannock River, Chesapeake Bay, USA

Human development has eroded Chesapeake Bay\u27s health, resulting in an increase in the extent and severity of hypoxia (≤2 mg O2 l-1). The Bay\u27s hypoxic zones have an adverse affect on community function and secondary production of macrobenthos. The production of macrobenthos is important as these fauna link energy transfer from primary consumers to epibenthic predators and demersal fish, and serve as the foremost pathway that carbon is recycled out of the sediment. Additionally, bioturbation, an essential macrobenthic function that causes the displacement and mixing of sediment particles, increases the quality of marine sediments. In the marine environment bioturbation is primarily mediated by macrofauna which are susceptible to perturbations in their surrounding environment due to their sedentary life history traits. The effect of hypoxia on macrobenthic production was assessed in Chesapeake Bay and three of its tributaries (Potomac, Rappahannock, and York rivers) from 1996 to 2004. Each year, 25 random samples were collected from each system and macrobenthic production estimated using Edgar\u27s allometric equation. Efforts were then focused on the Rappahannock River, a sub-estuary of Chesapeake Bay known to experience seasonal hypoxia, to assess changes in macrobenthic production and function. During the spring, summer, fall, and following spring of 2007 and 2008, samples were collected each season in each year, and DO concentrations were measured continuously at two sites in 2007 and two in 2008. A benthic observing system (Wormcam) was also deployed in 2009 from early spring to late fall to assess the impact of hypoxia on bioturbation. Wormcam transmitted a time series of in situ images and water quality data in near real-time. Results from the previous projects was used to develop a continuous-time, biomass-based model, including phytoplankton, zooplankton, and macrobenthic state variables. The primary focus aimed at predicting the effect of hypoxia on macrobenthic biomass. Z\u27, a sigmoid relationship between macrobenthic biomass and DO concentration, was derived from macrobenthic data collected from the 2007 and 2008 field experiments. Annual fluctuations in macrobenthic production were significantly correlated with DO. Hypoxia led to a 90% reduction in daily macrobenthic production relative to normoxia, and production at hypoxic sites was composed primarily of smaller, disturbance-related annelids. The reduced production resulted in an annual biomass loss of approximately 7320 to 13,200 metric tons C, which equated to a 6 to 12% annual displacement of the Bay\u27s total macrobenthic productivity due to hypoxia. Macrobenthic production differed across seasons, and sediment reworking rates were significantly higher during normoxia, indicating a change in the functional role of the macrobenthic community. Hypoxia was found to significantly reduce bioturbation through reductions in burrow lengths, burrow rates, and burrowing depth. Although infaunal activity was greatly reduced during hypoxic and near anoxic conditions, some individuals remained active. The biomass-based model was successfully calibrated and verified, using independent data, to accurately predict B annually. Simulation analysis of the DO formulation showed B strongly linked to DO concentration, with fluctuations in biomass significantly correlated with the duration and severity of hypoxia

Predicted sea-level rise-driven biogeomorphological changes on Fire Island, New York: implications for people and plovers

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zeigler, S. L., Gutierrez, B. T., Lentz, E. E., Plant, N. G., Sturdivant, E. J., & Doran, K. S. Predicted sea-level rise-driven biogeomorphological changes on Fire Island, New York: implications for people and plovers. Earth’s Future, 10(4), (2022): e2021EF002436, https://doi.org/10.1029/2021EF002436.Forecasting biogeomorphological conditions for barrier islands is critical for informing sea-level rise (SLR) planning, including management of coastal development and ecosystems. We combined five probabilistic models to predict SLR-driven changes and their implications on Fire Island, New York, by 2050. We predicted barrier island biogeomorphological conditions, dynamic landcover response, piping plover (Charadrius melodus) habitat availability, and probability of storm overwash under three scenarios of shoreline change (SLC) and compared results to observed 2014/2015 conditions. Scenarios assumed increasing rates of mean SLC from 0 to 4.71 m erosion per year. We observed uncertainty in several morphological predictions (e.g., beach width, dune height), suggesting decreasing confidence that Fire Island will evolve in response to SLR as it has in the past. Where most likely conditions could be determined, models predicted that Fire Island would become flatter, narrower, and more overwash-prone with increasing rates of SLC. Beach ecosystems were predicted to respond dynamically to SLR and migrate with the shoreline, while marshes lost the most area of any landcover type compared to 2014/2015 conditions. Such morphological changes may lead to increased flooding or breaching with coastal storms. However—although modest declines in piping plover habitat were observed with SLC—the dynamic response of beaches, flatter topography, and increased likelihood of overwash suggest storms could promote suitable conditions for nesting piping plovers above what our geomorphology models predict. Therefore, Fire Island may offer a conservation opportunity for coastal species that rely on early successional beach environments if natural overwash processes are encouraged.Funding for this work was provided by the U.S. Geological Survey's Coastal and Marine Hazards and Resources Program, with supplemental funding through the Disaster Relief Act

UAS-SfM for coastal research : geomorphic feature extraction and land cover classification from high-resolution elevation and optical imagery

© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Remote Sensing 9 (2017): 1020, doi:10.3390/rs9101020.The vulnerability of coastal systems to hazards such as storms and sea-level rise is typically characterized using a combination of ground and manned airborne systems that have limited spatial or temporal scales. Structure-from-motion (SfM) photogrammetry applied to imagery acquired by unmanned aerial systems (UAS) offers a rapid and inexpensive means to produce high-resolution topographic and visual reflectance datasets that rival existing lidar and imagery standards. Here, we use SfM to produce an elevation point cloud, an orthomosaic, and a digital elevation model (DEM) from data collected by UAS at a beach and wetland site in Massachusetts, USA. We apply existing methods to (a) determine the position of shorelines and foredunes using a feature extraction routine developed for lidar point clouds and (b) map land cover from the rasterized surfaces using a supervised classification routine. In both analyses, we experimentally vary the input datasets to understand the benefits and limitations of UAS-SfM for coastal vulnerability assessment. We find that (a) geomorphic features are extracted from the SfM point cloud with near-continuous coverage and sub-meter precision, better than was possible from a recent lidar dataset covering the same area; and (b) land cover classification is greatly improved by including topographic data with visual reflectance, but changes to resolution (when <50 cm) have little influence on the classification accuracy.This project was funded by the U.S. Geological Survey (USGS) Coastal and Marine Geology Program and the Department of the Interior Northeast Climate Science Center

Economic and Financial Methodology for South Texas Irrigation Projects – RGIDECON©

(originally published October 2002

An Overview of Operational Characteristics of Selected Irrigation Districts in the Texas Lower Rio Grande Valley: Delta Lake Irrigation District

Population expansion and water shortfalls have placed the Texas Lower Rio Grande Valley (Valley) center stage in water publicity. The unique characteristics and lack of public knowledge on how irrigation districts divert and convey water from the Rio Grande to municipal, industrial, and agriculture consumers have precipitated questions regarding the operations and makeup of these districts. Differences between and similarities across irrigation districts can be partially attributed to the topography, water-delivery infrastructure system, past financial decisions, and population demographics and clientele base of each irrigation district. Delta Lake Irrigation District (DLID) is one of the 29 irrigation districts in the Valley. This study presents an overview of DLID that includes a brief historical background, a description of the District, and discussion of the District’s current operations. Specific information in the report details how the District diverts and delivers its allocated water from the Rio Grande, how it is used (i.e., municipal, industry, and agriculture), and mechanisms for allocation within and outside the District. The uniqueness of the Lower Rio Grande Valley irrigation districts requires an understanding of their origins and operating mannerisms to explain their overall institutional effects. Through unlocking some of the conundrum associated with these individual irrigation districts, policymakers and other interested stakeholders will have a better perception of the culture and evolution that surround these unique districts, thereby facilitating improved policy-making decisions affecting the region’s water supply and usage

An Overview of Operational Characteristics of Selected Irrigation Districts in the Texas Lower Rio Grande Valley: Harlingen Irrigation District Cameron County No. 1

Population expansion and water shortfalls have placed the Texas Lower Rio Grande Valley (Valley) center stage in water publicity. The unique characteristics and lack of public knowledge on how irrigation districts divert and convey water from the Rio Grande to municipal, industrial, and agricultural consumers have precipitated questions regarding the operations and makeup of these districts. Differences between and similarities across irrigation districts can be partially attributed to the topography, water-delivery infrastructure system, past financial decisions, and population demographics and clientele base of each irrigation district. Harlingen Irrigation District Cameron County No. 1 (HIDCC1) is one of the 29 irrigation districts in the Valley. This study presents an overview of HIDCC1 that includes a brief historical background, a description of the District, and discussion of the District’s current operations. Specific information in the report details how the District diverts and delivers its allocated water from the Rio Grande, how it is used (i.e., municipal, industry, and agriculture), and mechanisms for allocation within and outside the District. The uniqueness of the Lower Rio Grande Valley irrigation districts requires an understanding of their origins and operating mannerisms to explain their overall institutional effects. Through unlocking some of the conundrum associated with these individual irrigation districts, policymakers and other interested stakeholders will have a better perception of the culture and evolution that surround these unique districts,thereby facilitating improved policy-making decisions affecting the region’s water supply and usage

Economies of Size in Municipal Water-Treatment Technologies: A Texas Lower Rio Grande Valley Case Study

As the U.S. population continues to increase, the priority on planning for future water quantity and quality becomes more important. Historically, many municipalities have primarily relied upon surface water as their major source of drinking water. In recent years, however, technological advancements have improved the economic viability of reverse-osmosis (RO) desalination of brackish-groundwater as a potable water source. By including brackishgroundwater, there may be an alternative water source that provides municipalities an opportunity to hedge against droughts, political shortfalls, and protection from potential surfacewater contamination. In addition to selecting a water-treatment technology, municipalities and their associated water planners must determine the appropriate facility size, location, etc. To assist in these issues, this research investigates and reports on economies of size for both conventional surface-water treatment and brackish-groundwater desalination by using results from four water-treatment facilities in the Texas Lower Rio Grande Valley (LRGV). The methodology and associated results herein may have direct implications on future water planning as highlighting the most economically-efficient alternative(s) is a key objective. In this study, economic and financial life-cycle costs are calculated for a “small” conventional surface-water facility (i.e., 2.0 million gallons per day (mgd) Olmito facility) and a “small” brackish-groundwater desalination facility (i.e., 1.13 mgd La Sara facility). Thereafter, these results are merged with other, prior life-cycle cost analyses’ results for a “medium” conventional surface-water facility (i.e., 8.25 mgd McAllen Northwest facility) and a “medium” brackish-groundwater desalination facility (i.e., 7.5 mgd Southmost facility). The combined data allow for examination of any apparent economies of size amongst the conventional surface-water facilities and the brackish-groundwater desalination facilities. This research utilized the CITY H20 ECONOMICS and the DESAL ECONOMICS © © Excel® spreadsheet models developed by agricultural economists with Texas AgriLife Research and Texas AgriLife Extension Service. The life-cycle costs calculated within these spreadsheet models provide input for work which subsequently provides the estimations of economies of size. Although the economies of size results are only based on four facilities and are only applicable to the Texas LRGV, the results are nonetheless useful. In short, it is determined that economies of size are apparent in conventional surface-water treatment and constant economies of size are apparent in brackish-groundwater desalination. Further, based on modified life-cycle costs (which seek to more-precisely compare across water-treatment technologies and/or facilities), this research also concludes that reverse-osmosis (RO) desalination of brackish-groundwater is economically competitive with conventional surface-water treatment in this region