We’ve seen reports that the blue crab population is up this season, and activity has certainly increased in Antipoison Creek compared to recent years. We have at least three crabbers with pots at the mouth of the creek, collecting bushels of crabs in the double digits many days. We’re about halfway through the crabbing season, which is when the Chesapeake Bay Stock Assessment Committee (CBSAC) releases their advisory report each summer on blue crabs. Made up of state agencies and scientists from Maryland and Virginia, the most recent publication, issued June 30, echoes other recent reports we’ve read about crab population abundance.
One thing the CBSAC highlights is the abundance of female crabs in the Bay (which gives an indication of how the overall population will look in the next year). The committee keeps track of population estimates for adult female crabs, juvenile crabs, and male crabs in the Bay. The committee also sets threshold limits and targets for adult female population numbers. The threshold limit, the point at which the adult female population should not fall below, is set at 70 million; the target is set at 215 million.
This year at the beginning of the harvest season, the committee counted an estimated 194 million spawning age female crabs, which is a 92% rise from last spring’s count. Because only 15% of adult females were harvested last year, which was below the 25.5% harvest target, and given that 194 million adult females is well above the 70 million threshold, the Stock Assessment Committee has declared that overfishing is not occurring in the Bay.
However, the count of adult females is still something to look out for, regardless of how well the population is doing this year, especially as the current season continues. The CBSAC points out that it was only two years ago when the adult female crab population dropped below the 70 million-threshold mark. Blue crab population numbers can be extremely variable, so a good harvest and population one year does not ensure healthy numbers for the next season.
The CBSAC report includes a list of recommendations to continue to support and increase the blue crab population, which includes expanding blue crab sanctuaries in Virginia (Lower Bay), Maryland (Upper Bay), and parts of the Potomac River (overseen by the Potomac River Fisheries Commission) to protect females of spawning age. The CBSAC also calls for improvements in surveys and data acquisition needed to make more informed estimates of current population numbers. One other recommendation made by the commission, dependent on further assessment, is instating an annual total allowable catch (TAC), which is a fisheries method we will go into more detail on here shortly.
You can check out the full CBSAC 2016 report here.
We have submerged aquatic vegetation growing off of both sides of our dock this year on Antipoison Creek for the first time in decades. This observed growth follows reports from the Virginia Institute of Marine Science (VIMS) that the acreage of submerged aquatic vegetation in 2015 Bay-wide significantly increased. Acting as a source of habitat for marine species, such as juvenile blue crabs (which we’ve also seen a lot of this year), it’s nice to see even a little improvement in SAV acreage in our local waters.
Using information from VIMS and the Chesapeake Bay Program, I think this specific grass is Ruppia maritima, commonly known as widgeon grass. While there are several species of submerged aquatic vegetation in the Chesapeake Bay Watershed, widgeon grass and eelgrass are two of the most commonly found species, since they can tolerate a range of salinities. Widgeon grass, according to the Chesapeake Bay Program, typically grows in the slightly brackish to salty waters in the upper, middle and lower reaches of the mainstem of the Bay, but can also be found in freshwater tributaries.
I tried to take underwater photos but the water was too murky today for anything to turn out. However, I’ve included photos of the grasses from above, and a strand of the grass laid out to see what it looks like up close.
Check out today’s front page article, “There’s Always a Catch,” on Chesapeake blue crabs in the Washington Post. Improvements in Bay water quality this year has had a positive impact on underwater grasses and blue crabs, but what does this mean for the Bay’s watermen? Journalist Steve Hendrix spent a day with a commercial crabber and found out temporary crab abundance doesn’t necessarily result in positive outcomes for our local watermen.
Each year, the University of Maryland Center for Environmental Science, the University of Michigan, and the National Ocean and Atmospheric Association collaborates on models predicting the size of the dead zone that will be found in the main stem of Bay over the summer months. Using USGS data on nutrient and sediment loads entering the Bay from the first half of this year, the models can pretty accurately predict how big this dead zone will be. This year’s prediction: the dead zone will be “slightly smaller-than-average.”
Please see the Chesapeake Bay Program for more information.
This spring we’ve read reports from the Virginia Institute of Marine Science (VIMS) on the recent resurgence of submerged aquatic vegetation in the Bay; we’ve seen the latest survey from VIMS and the Maryland Department of Natural Resources showing that blue crab populations are higher this year than in several years past; and we’ve seen the University of Maryland (UMCES) report on the overall improving water quality in the Bay watershed. We’ve noticed some of these improvements firsthand in Antipoison Creek, on Virginia’s Northern Neck. Gary Greenwood shares his observations below:
We just spent three days at our place in White Stone. The weather was terrific, but better than that, we saw things in and around the water that we haven’t seen in the 10 years we have been visiting.
Walking out our dock on Antipoison Creek we noticed a lot of underwater grasses growing on both sides. I understand from our neighbor who has lived on the creek for decades that there used to be a lot of underwater grasses in the creek, but it has been gone for a long time.
The grasses must be providing good habitat for young crabs. We have seen lots of skate in the shallows near the grass, and further out we see crab pots set by five different watermen, based on the colors of the buoys. We have always had crabs of course, but seldom a population to support this many pots.
We visited Mike next door at his oyster farm (www.windmilloysters.com). He was too busy getting a shipment of 5,000 oysters out the door, but he did give us some baby oysters so we can start the next generation in the cage under our dock. Mike said he is shipping more than 15,000 oysters a week, which is great for him and his small operation.
In addition to being a good business, Mike’s oyster farm, with a couple of million oysters in the creek and out in Little Bay, is probably one of the reasons the underwater grasses are returning. (See the earlier post about recent water quality in the creek and Little Bay.)
In the evenings I have been reading Kate Livie’s very enjoyable book, Chesapeake Oysters, about the oysters in the Bay and the people who have made a living from them. She does a great job recounting the history of the oyster from the 1600’s to the present. I hope to finish it this weekend.
One of our goals each time we visit is to eat local seafood whenever we can. This weekend we enjoyed roast oysters at Merroir across the river in Topping, and local rockfish from our fishmonger, Blue Water Seafood in Kilmarnock.
The efforts to clean up the Bay certainly need to continue. We plan to continue monitoring the water quality and donating our information and other resources where we think we can make a difference. This weekend has given us a little optimism that the things everyone does to help the Bay can make a difference.
The University of Maryland’s Center for Environmental Science (UMCES) recently released their report card on the health of the Chesapeake Bay for 2015. The Bay watershed received a grade of a C, which in comparison to past years, is pretty good. Last year’s grade was a D+; the Bay has not received a grade at or higher than a C since 2002.
The score is calculated by analyzing measurements and factors throughout the different segments of the Bay such as streamflow, fish populations, water clarity, levels of nutrients (total nitrogen and phosphorus), acreage of underwater grasses, types and levels of benthic macroinvertebrates, levels of dissolved oxygen and chlorophyll. Each of the following segments of the Bay receives a grade, and the overall score is an average of these areas (individual grades can be found on page 4 of the report).
The segments of the Bay that were analyzed and scored are:
- Upper Western Shore
- Upper Bay
- Patapsco and Back Rivers
- Lower Western Shore (MD)
- Upper Eastern Shore
- Patuxent River
- Choptank River
- Potomac River
- Lower Eastern Shore (Tangier)
- Rappahannock River
- Mid Bay
- York River
- Lower Bay
- James River
- Elizabeth River
Improvements were found for almost all of the measurements listed above, compared to recent years. Total phosphorus levels in the Bay, however, increased from last year, despite models showing a decrease in phosphorus loadings from tributaries. Further study is needed to explain this.
UMCES points out that only two other years – 2002 and 1992 – had scores as good as 2015. However, 2002 and 1992 were drought years, while 2015 was not. (Drought years are generally good years for water clarity, and nutrient and sediment levels, as there is less runoff entering and polluting the Bay and Bay tributaries). So a question this latest report leaves us with is: Is water quality in the Bay improving? Or is the higher score attributed to other factors, such as the milder water temperatures of last summer?
By Libby Warner
The University of Maryland Center for Environmental Science’s (UMCES) Chesapeake Biological Laboratory (CBL) on Solomon’s Island is a research facility where scientists study various aspects of ecosystems, including restoration ecology, toxicology, and fisheries. On Monday, May 16th, I had the opportunity to visit the center and learn about the different projects taking place on a very informative and inspiring tour given by the CBL Director, Dr. Thomas Miller. Upon arrival, I immediately was struck with the beauty of the location. Red brick buildings with many windows overlook the Patuxent River, which feeds into the Chesapeake Bay. There is a grand, gated-off research pier that extends out into the river and contains a Pump House, which transfers water to various laboratories for testing.
The first stop we made on our tour was the Nutrient Analytical Services Laboratory that tests water quality. This laboratory consists of approximately seven full time scientists whose job is to run water samples through extensive tests that indicate the levels of various chemicals such as phosphorus or nitrogen. These samples can come from a variety of places, ranging from creeks to oceans, and therefore the analysis of these water samples varies. There are two primary methods used for these chemical tests. One method involves a spectrophotometer that relies on robotics and allows very small water samples to be used. The other method is less advanced and has existed since the 1970’s. It involves a complex tubing mechanism that relies on a very specific air pressure system with air bubbles existing every few centimeters in the tubes. This method requires larger water samples, but is beneficial in that it helps the operator gain a better understanding of how the system works. In some instances, it also gives a more accurate reading than the robotics system.
The next stop we made was in the “crabs on acid” laboratory. This lab is used for research on the effects of ocean acidification on blue crab populations in the Chesapeake Bay. A PhD candidate, Hillary Glandon, conducts this research. There are a few large tanks hooked up to the piping system, which collects water from the Patuxent River. The piping system has two pipes, which are alternatingly utilized to prevent the buildup of sediment and barnacles. The large tanks of river water in the laboratory act as different treatment groups, each with a different pH, which is controlled by adding different amounts of CO2. Each large tank feeds into multiple smaller tanks, which host the blue crabs. Originally, the proposed thesis was to determine the effect of ocean acidification on crab shell growth. However, with blue crab shells being difficult to measure due to the molting process that they undergo, Hillary altered her experimental question and is now studying the effect of acidification on blue crab respiration rates. (Lab pictured below).
After our stop at the blue crab laboratory, we went to a laboratory that measures methane levels in samples of water from the tropics. Another UMCES graduate student pursuing her PhD, Hadley McIntosh, conducts this research. These specific laboratories were a few of the many sites of research at UMCES. There are approximately 20 graduate students currently attending the university in addition to at least a dozen other full time employees who help provide nutrient analytical services. An interesting statistic regarding this gradate program is that about 65% of the students are women.
Overall, this visit inspired me, not only as a science student, but also as a member of the millennial generation. We are a generation of rising world leaders and it will be our responsibility to restore our planet’s environment after the damage it has received from prior generations. Research facilities such as this one on Solomon’s Island give me hope that, with the existence of strong, innovative scientific communities such as this one, we may have a shot at a brighter future.
The author, Libby Warner, our new contributor to the blog, pictured below, collecting water samples on the Chesapeake Bay:
We’ve been working with the Nutrient Analytical Services Laboratory (NASL) at the University of Maryland Center for Environmental Science’s Chesapeake Bay Laboratory for several months now, analyzing water quality in the Potomac River and Antipoison Creek (a small tributary of the Chesapeake Bay on Virginia’s Northern Neck). NASL provides the analytical services for phosphates, nitrates, ammonium, and various forms of chlorophyll (total, active, and phaeophtin), from water samples that we collect, and filter in preparation for analysis. We also measure pH and salinity of these samples. For more on procedures, please see my previous post here.
The sampling sites on the Potomac River are found just north of Riverbend Park’s visitor center. Samples here are collected on foot, with a swing sampler, at three locations (with two samples taken per location, samples “A” and “B” in the data shown below). The Antipoison Creek samples are taken via boat at five or six locations(also with two samples taken per location). Sampling is generally conducted once a month on both bodies of water, or after an extreme precipitation event. Sampling began on Antipoison Creek this past September, and on the Potomac River this past January.
Now that we have a few months of data, we would like to share them here.
The following is ammonium (NH4), phosphate (PO4), and nitrate (NO23) levels, and their averages, at Antipoison Creek from September to December of 2015. We did not start testing for chlorophyll until December of 2015, and only have one month’s worth of data for those parameters.
The following is ammonium (NH4), phosphate (PO4), and nitrate (NO23) levels, and their averages, on the Potomac River from January and February from this year.
Comparing between sampling locations, ammonium, phosphate and nitrate averages from the Potomac River samples are significantly higher than the Antipoison Creek samples. The Antipoison Creek watershed is rural. There is some agriculture going on in the fields surrounding the creek, along with low-density residential development. Antipoison has a great deal of oyster aquaculture taking place within the creek, with personal oyster floats off residential properties, and a commercial production facility located at the mouth of the creek (with thousands of oysters being grown in the vicinity). This is likely having a significant impact on water quality.
The Potomac River watershed, in the area where we are testing, is much more densely populated. Nutrient levels, such as phosphates and nitrates, might be higher due to higher concentrations of polluted runoff coming from suburban developments. There are also no oysters acting as a natural filtration system in this part of the watershed. It will be interesting to compare chlorophyll levels between these locations once enough data is retrieved and analyzed. We’ll keep you posted!
Surveys for both blue crabs and underwater seagrass found increases in population levels and acreage in the Chesapeake Bay this year.
The 2016 joint survey between the Maryland Department of Natural Resources and the Virginia Institute of Marine Science (VIMS) found that there are 35% more blue crabs in the Bay than this time last year. More specifically, the female population reached 194 million individuals, with overall numbers reaching 553 million.
Crab population numbers tend to fluctuate year-to-year, based on a number of factors, such as habitat loss, water temperatures, and harvest levels. The past two years have seen improvements to population numbers, but the blue crab is still considered to be in a state of recovery. Numbers have not reached 800 million, the number of blue crabs found after the first survey in 1988, in many years. With population fluctuation in mind, experts at the Smithsonian Environmental Research Center stated that this year’s good news does not necessarily mean that stricter harvest restrictions in Virginia and Maryland should be lifted. (SERC, 2016).
Crab population levels can be linked to seagrass acreage in the Bay. Seagrass provides habitat and protection for juvenile blue crabs. In past years, seagrass loss has been one predicted cause for blue crab population declines. The most recent survey from VIMS found that Bay seagrass acreage in 2015 was the highest it has been in 30 years. Perhaps these increases correlate to blue crab numbers.
The VIMS survey counted 91,631 acres of seagrass, up 21% from the 2014 survey, and 140% from the first survey in 1984. For more information on growth rates in specific regions (Upper Bay, Mid Bay, Lower Bay), please see the Bay Journal.
The Potomac Conservancy has released their biennial report on the Potomac River, the second largest river draining into the Chesapeake Bay. The health of the Potomac River, due to its large area and population size within watershed boundaries, is very important to the health of the Bay. The Potomac Conservancy has issued the River a grade of B- in terms of overall health. Rising from a D to a C to a B- over the past ten years, the state of the Potomac River is improving. However, a number of different areas need to be addressed to continue to improve water quality in the Potomac and the Chesapeake.
Figures 1, 2, and 3 show changes to nitrogen, phosphorus and sediment loads in the Potomac from 1985 to 2014. Over this time period, there have been load reductions from these three major sources of pollution.
The improvements in overall health of the Potomac River are due in large part to reduced sediment and nutrient loads from agricultural activity and wastewater treatment plants.
Wastewater treatment facilities have undergone a number of upgrades to ensure that water discharged from facilities contains smaller concentrations of nitrogen and phosphorus. With higher standards now required by the EPA, upgrades to many wastewater treatment facilities in the watershed have contributed to cleaner waters in the Potomac River. (Between 2011 and 2015, there was a 13% increase in facilities adhering to stricter EPA standards).
Agriculture in the Potomac River watershed has likely contributed fewer nutrient loads because agricultural activity within the region is declining, as land is converted to accommodate urban sprawl. The Potomac River, which flows from Fairfax Stone, West Virginia to Point Lookout, Maryland, covers a large urban and suburban area. So, while agricultural runoff is decreasing, nitrogen and phosphorus loads in stormwater runoff from developed areas is still a major concern.
Within this report, the Potomac Conservancy grades a number of sub-indicators of river health, such as fish population, underwater grass abundance, and recreational use. These ratings are then examined together to determine overall health. While overall health of the river is improving, there are some areas that are actually doing worse, or showing no marked improvement from previous years. This is the case for water clarity and underwater grass abundance, which received a grade of C-. These two factors are important indicators of health in the Chesapeake Bay (underwater grasses provide food and habitat for marine species, and filter sediments and nutrients in the water, which can improve water clarity). Going forward, I would definitely like to see higher rates of recovery for these two indicators.
There is mixed news for the river’s fish populations. Certain species, such as shad, white perch, and smallmouth bass are experiencing population growth. The Bay’s rockfish population, however, has declined slightly over the past ten years. Many fish species are at continued risk of predation from invasive species such as the blue catfish and snakehead.
In terms of tidal water quality, certain conditions are improving, although numbers for dissolved oxygen, clarity, and chlorophyll A (a measure of algae), vary year to year. Chlorophyll A levels have declined over the last fourteen years. See Figure 4 below.
[We have been taking water samples from both the Potomac River (out of Great Falls), and Antipoison Creek, (which is just off of the Chesapeake Bay, close to where the Rappahannock River meets the Bay), and interestingly, found higher chlorophyll levels in Antipoison Creek. I’ll post more on our results later.]
There was good news for recreational land use, which has gone up since the last report. Recreational use of waterways can be an indicator of improved water quality.
Protected land area has increased, from 1.8 million acres in 2011 to 1.9 million acres in 2013. This area equates to 26.6 percent of land in the Potomac River watershed.
Concerns going forward include rates of deforestation and development in unsuitable areas, and runoff from suburban and urban regions. Agricultural areas, while declining, could still do with the enforcement of Best Management Practices (BMPs). The amount of forested buffers (streamside vegetation which reduces agricultural runoff into tributaries), received a grade of C-.
It’s important to keep in mind that the results in this report do not come from the most current data. The Potomac Conservancy gathers its information from a number of institutions, such as the EPA and the USGS. There is a couple years lag time on data for many of these sub-indicators of overall health.
Information and graph source: State of the Nation’s River 2016, Potomac River Conservancy, http://potomacreportcard.org.