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Chesapeake Bay News: Science

Jun
30
2017

Photo of the Week: Growing CommuniTree in West Virginia

Danielle French, right, and Roanin Cabrera plant a tree at Deerfield Village outside of Shepherdstown, West Virginia, at an event on April 29, 2017. Adult and youth volunteers planted 28 trees as part of the Carla Hardy West Virginia Project CommuniTree program.

CommuniTree is an initiative of the Cacapon Institute—a watershed protection organization located in Great Cacapon, West Virginia—and is the largest tree steward program in the state. The purely-volunteer program promotes tree planting and education on the public lands that surround the headwaters of the Potomac River.

This spring’s tree planting event marked the fourth one held at Deerfield Village, following plantings in 2014, 2015 and 2016. Of the 72 trees planted during those prior events, 60 have survived to provide clean air, shade and other benefits to their communities. This year, volunteers planted 12 trees to replace those that had failed to establish, as well as 16 new trees as part of an old apple orchard.

Trees are a critical piece of a healthy ecosystem: they soak up polluted stormwater, provide habitat for wildlife, absorb and trap air pollution and enhance quality of life for local communities. That’s why Chesapeake Bay Program partners have committed to expanding tree canopy in urban areas by 2,400 acres by 2025, providing air quality, water quality and habitat benefits throughout the Chesapeake Bay region.

Learn more about CommuniTree, or learn about our work to increase tree canopy in the watershed.

Image by Will Parson

Stephanie Smith's avatar
About Stephanie Smith - Stephanie is the Web Content Manager at the Chesapeake Bay Program. A native of the Midwest, she received her Bachelor’s in Professional Writing from Purdue University and Master of Science degree from the University of Michigan. Stephanie’s lifelong love of nature motivates her to explore solutions to environmental problems and teach others what they can do to help.



Jun
29
2017

From the Field: How invasive species could be impacting vital salamander habitat

Within five minutes of entering Corcoran Woods, Susan Lamont is bent over what looks like a large puddle, gently holding a gelatinous mass. The mass is made up of salamander eggs, and what she’s bent over is no puddle, but a vernal pool.

Vernal pools are ephemeral forest ponds, fed by snow, rain or groundwater. They only stay wet for about seven months out of the year, but in that time, they host a wealth of animals. Amphibians like salamanders and frogs lay their eggs in vernal pools, which have fewer predators like fish due to their temporary nature.

Today, Lamont, a biology professor at Anne Arundel Community College, is leading a group of students and volunteers in a survey of vernal pools, looking for egg masses lain by spotted and marbled salamanders. They’re exploring the more than 200-acre Corcoran Environmental Study Area, which lies in Anne Arundel County, Maryland, just west of the Chesapeake Bay.

Anne Arundel Community College student Dominic Ollivierre, right, pulls leaves from a net while surveying a vernal pool with classmates and biology professor Susan Lamont, second from left, at Corcoran Woods, part of Sandy Point State Park in Anne Arundel County, Md., on March 24, 2017. For three years, Lamont has brought her students and volunteers out to survey the woods’ vernal pools.

The southeastern section of Corcoran Woods is dotted with these temporary pools. Lamont breaks the students up into groups and shows them the pools they’ll be surveying. Armed with nets, boots and GPS markers, they begin scouring their pools for evidence of amphibian breeding.

Along with the surveying that her students and volunteers are doing, Lamont is setting traps for adult salamanders to help determine how they use the pools. In the past, she and her students would find adults by looking under rocks and logs. “I want to know how much they’re using the pools,” she says.

Now in her third year of the study, Lamont’s research not only answers her own questions and provides her students with an outdoor learning opportunity, it also serves the Maryland Department of Natural Resources (DNR), which owns Corcoran Woods. They were concerned about the vernal pools and if they were at risk of drying up. “If you’re managing the pools, you have to know what’s happening with them,” says Lamont. “They don’t have the staff to come out and do [the surveying], and it’s easy to get the students—they love it.”

A spotted salamander egg mass develops in a vernal pool at Corcoran Woods. Anne Arundel Community College biology professor Susan Lamont is studying the impact on vernal pools at Corcoran following the removal of invasive plants.

About a half mile away, the northwest corner of the forest tells a different story. There are no vernal pools here, but there is an even more dramatic difference: this corner of the woods, unlike the southeast where Lamont’s students are surveying, is plagued by invasive species.

Much of the land was cleared of invasives last year, treated with herbicides and replanted with native trees. The hope is that the natives will grow large enough to shade the area and help keep invasives out. Until then, it will have to be carefully looked after to prevent regrowth of invasive species.

A slight turn in the trail reveals the vastly altered landscape. A forest of plastic tree tubes blankets the area of what used to be acres of invasive plants like oriental bittersweet, English ivy and multifloral rose. Some original trees still remain, but pale-green tubes stick out like hundreds of hair plugs.

Susan Lamont, a biology professor at Anne Arundel Community College, stands at the edge of a large invasive species removal and tree planting site at Corcoran Woods.

“The red plot was severely infested,” recalls Lamont. “Before they treated it, all you could see were invasives. Vines were over the tops of the trees.” Thick vines still hung from a few of the remaining trees, but hovered about six feet above the ground where they had been severed from their roots.

Along with sunlight, invasive species require a lot of water, and in turn could have lowered the groundwater table. “This is a drier area than the vernal pool area,” Lamont notes. “We’re not sure if it’s drier because [the invasive species] were here, or if that’s why the invasives took over.” If the former is true, it could spell bad news for the vernal pools if the invasive species make their way south east.

Groundwater is generally talked about in terms of drinking water and irrigation, but forest plants and animals need it just as much as humans. In Corcoran Woods, groundwater is vital for feeding the vernal pools that salamanders and other amphibians rely on, but this corner of the woods is much drier and noticeably absent any pools.

That’s where Lamont’s new research comes in. She’s going to put groundwater monitoring wells in the area where the invasives are to see if the removal efforts make the area wetter. She’ll also put some groundwater wells in the vernal pool area to compare water levels within Corcoran Woods.

“[Maryland DNR is] very interested in protecting the pool habitat and restoring the part of the woods that was decimated by invasives,” Lamont says. By measuring the effect of invasive species on groundwater—and, in turn, the vernal pools the salamanders use—Lamont and her students can help DNR support the interconnected ecosystem at Corcoran Woods.

Images by Will Parson

Joan Smedinghoff's avatar
About Joan Smedinghoff - Joan is the Communications Office Staffer at the Chesapeake Bay Program. Originally from Chicago, she was introduced to the Chesapeake Bay region through the streams of central Pennsylvania. She received her Bachelor's in Environmental Studies from Dickinson College in Carlisle, Pa., where she first discovered her passion for storytelling.



Jun
29
2017

By the Numbers: 23

In our watershed, a fish that is no more than 10 inches long is a sentinel of climate change. Because brook trout need cold, clean water to survive, their presence in the region’s headwaters is a sign of stream health. As urbanization and other factors have raised the temperature of streams across the region, scientists have documented the disappearance of this sensitive fish. But experts now believe future increases in stream temperature will be less uniform than once thought, marking a shift in our understanding of how climate change could impact the only native trout in the Chesapeake Bay watershed.

The single most important factor in predicting whether brook trout will inhabit an area is water temperature.

According to the Eastern Brook Trout Joint Venture, brook trout began to disappear from the region when early agriculture, timber and textile industries prompted the removal of forests and pollution of streams. Today, urbanization threatens remaining brook trout habitat: paved surfaces push sediment into waterways, while dams and poorly designed culverts isolate brook trout populations from one another. The large, non-native brown trout—which is often stocked in rivers and streams to support fly fishing—has also been found to out-compete brook trout.

However, the single most important factor in predicting whether brook trout will inhabit an area is water temperature. While individual brook trout populations can acclimate to regional water temperatures, brook trout experience stress when stream temperatures reach 20 degrees Celsius and are typically absent when temperatures exceed 23 degrees. Scientific consensus has placed the limits of brook trout survival between 0 and 23 degrees Celsius (about 32 and 73 degrees Fahrenheit).

In Maryland and Virginia, high water temperature has been named the greatest disturbance to brook trout populations. In light of this fact, the National Park Service and U.S. Geological Survey (USGS) have supported efforts to predict how climate change will impact brook trout habitat in two national parks in an attempt to resolve the uncertainties of our changing environment at a scale that would be relevant to natural resource managers.

Field work at Shenandoah National Park has helped researchers realize that future increases in stream temperature will be less uniform than once thought, marking a shift in our understanding of how climate change could impact brook trout habitat. Photo by Ken Lane/Flickr.

Craig Snyder and Nathaniel Hitt are researchers at the USGS Leetown Science Center. Through field work in Shenandoah National Park and statistical modeling and simulation, Snyder and Hitt found that climate change would not affect brook trout habitat in the way previous research has largely assumed. Instead, the localized upwelling of cold groundwater into streams will create a varied pattern of stream temperatures and a patchy distribution of suitable brook trout habitat.

“We’ve learned that you need to account for groundwater to anticipate stream responses to climate change,” Snyder said. “The future will be more complicated—and thermally fragmented—than prior research has recognized.” In other words, as the region experiences more widespread effects of climate change, the temperature-related fragmentation of brook trout habitat will play a bigger role in determining the viability of the region’s brook trout populations.

While accounting for the effects of cold groundwater on stream temperature make Snyder and Hitt’s predictions less pessimistic than some others, all of their scenarios predict habitat loss in Shenandoah National Park. “The general consensus is that a 1.5-degree Celsius increase [in the region’s mean annual air temperature] is unavoidable. The question is, will we hit 5 degrees Celsius? And if so, when?” Under such an increase, “basically all habitat [in the park] becomes unsuitable, regardless of groundwater effects,” Hitt said.

“Our research indicates that stream warming will not proceed in a systematic or spatially uniform way,” said Snyder. “It’s going to more closely resemble a shattering of thermal habitat than a systematic change.”

Brook trout that have responded at an evolutionary level to heat stress could be good candidates for reintroduction to historically occupied habitat. Photo by Dave Herasimtschuk/Freshwaters Illustrated.

Just what this “shattering” of suitable habitat will do to brook trout populations is unclear. While it is likely to diminish brook trout occupancy—or the presence of the fish in a particular area, which is used instead of the more variable abundance to determine the health of brook trout populations—some unknowns remain. For instance: what conditions will brook trout swim through in order to find suitable habitat? How much cold habitat is necessary for a self-sustaining brook trout population to thrive? And can local populations adapt to heat stress over time?

This kind of research could help our partners expand brook trout populations rather than merely holding onto the habitat that currently exists. If scientists find brook trout that have responded at an evolutionary level to heat stress, for example, they could use these populations to reintroduce fish to historically occupied habitat and, in turn, move closer to the Chesapeake Bay Watershed Agreement commitment to increase occupied habitat.

“This species has existed for millions of years,” Hitt said. “They’re survivors. A loss of a cohort in one year has little effect on population dynamics. But three or four back-to-back years of bad recruitment—that’s where the problem is. Our research helps us predict where brook trout populations will be more resilient to coming environmental changes.”

Snyder, Hitt and Zachary Johnson recently used remote sensing data to model the effects of groundwater on stream temperature. Their work showed that landform features and precipitation records can predict where groundwater affects fish habitat, and the results of this work have been mapped by the USGS Eastern Geographic Science Center.

“Our research shows that stream temperature data are valuable not only for understanding current thermal habitat conditions for brook trout, but also for anticipating future changes,” said Johnson. “Our work can help prioritize streams for long-term brook trout conservation.”

Learn more about the Chesapeake Bay Program’s work to restore and sustain brook trout in the region’s headwater streams.

Catherine Krikstan's avatar
About Catherine Krikstan - Catherine Krikstan is a web writer at the Chesapeake Bay Program. She began writing about the watershed as a reporter in Annapolis, Md., where she covered algae blooms and climate change and interviewed hog farmers and watermen. She lives in Washington, D.C.



Jun
26
2017

Blue crab stock considered sustainable, despite population decline

Fisheries experts have encouraged Maryland, Virginia and the Potomac River Fisheries Commission to take a cautious approach to blue crab management as they set harvest regulations for the coming year. In the annual Chesapeake Bay Blue Crab Advisory Report, these experts note that while the 2016 female blue crab harvest was lower than regulations require and the 2017 adult female blue crab population was above what is considered a healthy level, the overall blue crab population fell almost 18 percent in 2017.

In 2016, an estimated 16 percent of female blue crabs were harvested from the Chesapeake Bay. Experts say the stock is not depleted and overfishing is not occurring, but advise a cautious approach to blue crab management.

The Blue Crab Advisory Report is published by the Chesapeake Bay Stock Assessment Committee (CBSAC): a team of federal fisheries experts and scientists and representatives from state agencies and academic institutions. It is meant to provide resource managers with scientific data and advice.

According to the report, the start of the 2017 crabbing season saw an estimated 254 million adult female crabs in the Bay: a 31 percent increase from last year’s adult female blue crab abundance. Because this number is above the 215 million target and the 70 million threshold, the blue crab stock is not considered depleted. And because only 16 percent of the female blue crab population was harvested in 2016—which is below the 25.5 percent target and the 34 percent overfishing threshold—overfishing is not occurring. However, the overall blue crab population fell from 553 million to 455 million between 2016 and 2017.

“The highly variable nature of blue crabs was on full display this past year,” said CBSAC Chair Glenn Davis in a media release. “The largest abundance of spawning females from the Winter Dredge Survey time series was great news, and demonstrated what can happen when jurisdictions adhere to science-based management. The low recruitment [or number of young crabs entering the adult population] served as a reminder that large inter-annual fluctuations can be part of the norm and that managing blue crabs is a continuous challenge.”

In its report, CBSAC recommends:

  • A cautious, risk-averse approach to managing blue crabs. This could include scaling back fall fishery regulations in order to ensure more young crabs survive to spawn next season.
  • Improving the accuracy of tracking commercial and recreational crab harvests and exploring new reporting technologies.
  • Addressing specific research questions and discussing the timing, rationale and resources for future assessments of the blue crab stock to provide in-depth analyses of the blue crab population, fishery and management.

“The annual Blue Crab Advisory Report provides valuable data analysis and recommendations to the agencies that manage crabs here in the Bay to help them make scientifically informed decisions regarding our beloved—and valuable—blue crabs,” said Chesapeake Bay Program Sustainable Fisheries Goal Implementation Team Chair Sean Corson in a media release. “The science it features enables us to enjoy crabs…today and in future years.”

Learn more.



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