Considerations for Benthic Harmful Algal Bloom Detection and Monitoring in Virginia Free-flowing Freshwater Rivers (Version 1) Archives

Entry Thumbnail

Considerations for Benthic Harmful Algal Bloom Detection and Monitoring in Virginia Free-flowing Freshwater Rivers (Version 1)

The Commonwealth of Virginia currently does not have an active Harmful Algal Bloom (HAB) surveillance program for benthic algae. Rather, it has a response-based program triggered by reports of suspected benthic HABs from the public and/or field observations made by state agency staff. The Virginia Department of Health (VDH) coordinates the Commonwealth’s responses to suspected benthic HAB events. Virginia Department of Environmental Quality (DEQ) normally conducts the initial response to any potential HAB, which may include visits to the HAB site for visual observations and collection of water column samples above or near the benthic algal mats. DEQ does not collect algal material from solid mats, benthic or floating, and has limited resources to commit beyond the initial response investigation of reported potential HABs. VDH is charged with the responsibility to weigh the available evidence and determine whether there is sufficient information to issue an advisory or alert notifying the public of possible risk due to the presence of harmful algae.

Advisories may be issued based on confirmed, quantitative data such as an exceedance of a toxin threshold measured in the water column. Alerts may be based, partially or fully, on qualitative information such as the widespread presence, or suspected presence, and extent of solid floating/benthic mats or scums. The subsequent benthic HAB response monitoring program must therefore consider protocols to be implemented in both circumstances, i.e., an advisory based on confirmed, quantitative measurements versus a qualitative “abundance of caution” alert informing the public of a possible health risk.

This project report describes systematic protocols that could be implemented if an advisory or alert is issued by VDH for a benthic HAB event. The report identifies the information needed to issue an advisory or alert, the recommended actions, an effective schedule of activities, and the resources needed to characterize the nature and extent of the HAB and implement the protocols. The suggested monitoring program considers the conditions and information that led to the HAB advisory or alert. The report describes how decision-makers are informed of the health risks associated with recreational swimming, fishing, and other water contact activities.

Entry Thumbnail

Stream Biological Health in the Chesapeake Bay Watershed

To learn more about this project and find interactive maps, check out the webpage for “Chessie BIBI” Index for Streams .

Executive Report

This report offers a numeric value for the 2008 Baseline referenced in the 2014 Chesapeake Agreement’s stream health goal as well as evidence of a net improving trend in stream health in the Chesapeake watershed. The report demonstrates a process for tracking progress in achieving the stream health goal to “improve health and function of ten percent of stream miles above the 2008 baseline.” The bioregion, family-level version of the Chesapeake Basin-wide Index of Biotic Integrity, or “Chessie BIBI,” is used to quantify stream health. The index is calculated from macroinvertebrate data collected by state, federal, county, and volunteer monitoring programs with kick net methods and was developed specifically for 1st – 4th order streams in the Chesapeake watershed (Smith et al. 2017). The 2008 Baseline is the 2006 – 2011 period because it encompasses all sampling schedules of the watershed’s state monitoring programs, most of which employ rotational sampling.

Gaps in the monitoring data’s spatial and temporal coverage make it difficult to directly estimate percentages of healthy streams in the pre-baseline (2000 – 2005), baseline, and subsequent “first interval” (2012 – 2017) periods. Statistical analyses indicate approximately 61.7% (~89,317 miles) of non-tidal stream miles likely supported healthy macroinvertebrate communities in the baseline period. The percentage increased to 67.8% (~98,049 miles) in the first interval. Despite this roughly 6% net improvement, some areas of the watershed show degrading trends. The net improving trend, however, suggests the collective impact of multiple environmental stressors on streams may be slowly lessening in many parts of the Chesapeake watershed. Identifying which factors are responsible for the net improvement would be speculative at this point, although long-term efforts to conserve forests, preserve and restore riparian corridors and wetlands, mitigate acid rain and mine drainage, slow stormwater runoff, and reduce nutrients and sediment loads have all likely contributed. Metrics for a variety of environmental stressors are currently being explored and will help future investigations of stream macroinvertebrate responses to those stressors. They can help explain why the current trend is happening.

The purpose of this report is to present the monitoring-based results and provide CBP with a process for tracking progress in achieving the Chesapeake watershed’s stream health goal. The process differs in some respects from those of the state agencies who use the data differently and for state regulatory purposes. We fully expect the Chessie BIBI results will also differ from state results at times, even though the underlying raw data are the same. The Chessie BIBI can be used for inter-jurisdictional, watershed-based planning and evaluation.

Entry Thumbnail

Nutrient limitation of phytoplankton in three tributaries of Chesapeake Bay: Detecting responses following nutrient reductions

ABSTRACT: Many coastal ecosystems suffer from eutrophication, algal blooms, and dead zones due to excessive anthropogenic inputs of nitrogen (N) and phosphorus (P). This has led to regional restoration efforts that focus on managing watershed loads of N and P. In Chesapeake Bay, the largest estuary in the United States, dual nutrient reductions of N and P have been pursued since the 1980s. However, it remains unclear whether nutrient limitation – an indicator of restriction of algal growth by supplies of N and P – has changed in the tributaries of Chesapeake Bay following decades of reduction efforts. Toward that end, we analyzed historical data from nutrient-addition bioassay experiments and data from the Chesapeake Bay Long-term Water Quality Monitoring Program for six stations in three tidal tributaries (i.e., Patuxent, Potomac, and Choptank Rivers). Classification and regression tree (CART) models were developed using concurrent collections of water-quality parameters for each bioassay monitoring location during 1990-2003, which satisfactorily predicted the bioassay-based measures of nutrient limitation (classification accuracy = 96%). Predictions from the CART models using water-quality monitoring data showed enhanced nutrient limitation over the period of 1985-2020 at four of the six stations, including the downstream station in each of these three tidal tributaries. These results indicate detectable, long-term water-quality improvements in the tidal tributaries. Overall, this research provides a new analytical tool for detecting signs of ecosystem recovery following nutrient reductions. More broadly, the approach can be adapted to other waterbodies with long-term bioassays and water-quality data sets to detect ecosystem recovery.

See more on the ScienceDirect page.

Entry Thumbnail

Explainable machine learning improves interpretability in the predictive modeling of biological stream conditions in the Chesapeake Bay Watershed, USA

Anthropogenic alterations have resulted in widespread degradation of stream conditions. To aid in stream restoration and management, baseline estimates of conditions and improved explanation of factors driving their degradation are needed. We used random forests to model biological conditions using a benthic macroinvertebrate index of biotic integrity for small, non-tidal streams (upstream area ≤200 km2) in the Chesapeake Bay watershed (CBW) of the mid-Atlantic coast of North America. We utilized several global and local model interpretation tools to improve average and site-specific model inferences, respectively. The model was used to predict condition for 95,867 individual catchments for eight periods (2001, 2004, 2006, 2008, 2011, 2013, 2016, 2019). Predicted conditions were classified as Poor, FairGood, or Uncertain to align with management needs and individual reach lengths and catchment areas were summed by condition class for the CBW for each period. Global permutation and local Shapley importance values indicated percent of forest, development, and agriculture in upstream catchments had strong impacts on predictions. Development and agriculture negatively influenced stream condition for model average (partial dependence [PD] and accumulated local effect [ALE] plots) and local (individual condition expectation and Shapley value plots) levels. Friedman’s H-statistic indicated large overall interactions for these three land covers, and bivariate global plots (PD and ALE) supported interactions among agriculture and development. Total stream length and catchment area predicted in FairGood conditions decreased then increased over the 19-years (length/area: 66.6/65.4% in 2001, 66.3/65.2% in 2011, and 66.6/65.4% in 2019). Examination of individual catchment predictions between 2001 and 2019 showed those predicted to have the largest decreases in condition had large increases in development; whereas catchments predicted to exhibit the largest increases in condition showed moderate increases in forest cover. Use of global and local interpretative methods together with watershed-wide and individual catchment predictions support conservation practitioners that need to identify widespread and localized patterns, especially acknowledging that management actions typically take place at individual-reach scales.

Find more information on the ScienceDirect page.

Entry Thumbnail

Potomac River Water Quality at Great Falls: 1940 – 2019

The U.S. Army Corps of Engineers operates Washington Aqueduct and provides drinking water to the Washington, D.C. area. Washington Aqueduct routinely samples its source of water, the Potomac River. Each year, it reports the monthly averages for basic water parameters and several pollutants and metals. Reports since 2001 are available online. Reports from 1905 to 2000, however, had limited distribution and their legibility has faded over time.

Dr. Norbert A. Jaworski recognized the historical value of these reports. To prevent their loss, he digitized the monthly values for several parameters. The Interstate Commission on the Potomac River Basin (ICPRB) later updated his dataset through 2019 and checked the entered data for accuracy. This report focuses on changes in temperature, hardness, pH, total solids, chloride, nitrate, and sulfate over the 80 years since ICPRB was formed in 1940. Visual representations (“heatmaps”) and trend analysis show significant increasing trends in all these parameters except nitrate. The report is intended to introduce the historical Washington Aqueduct water quality data to a broader audience and highlight their potential value to Potomac studies.

The Supplemental Materials document contains additional graphical representations of the data.

See the video summary of the report: