Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. Earth Science News .




WATER WORLD
Research shows denser seagrass beds hold more baby blue crabs
by David Malmquist for VIMS News
Gloucester Point VA (SPX) Sep 18, 2013


VIMS marine scientist Kathleen Knick uses a suction sampler to count the number of juvenlie blue crabs in a Chesapeake Bay seagrass bed. Photo by Rochelle Seitz.

When it comes to nursery habitat, scientists have long known that blue crabs prefer seagrass beds compared to open areas in the same neighborhood.

A new study by researchers at the Virginia Institute of Marine Science refines that knowledge, showing that it's not just the presence of a seagrass bed that matters to young crabs, but also its quality-with denser beds holding exponentially more crabs per square meter than more open beds where plants are separated by small patches of mud or sand.

The study, led by VIMS graduate student Gina Ralph, appeared in the August issue of Marine Ecology Progress Series. It is co-authored by VIMS Marine Scientist Kathleen Knick along with faculty members Rochelle Seitz, Robert "JJ" Orth, and Rom Lipcius.

"Vegetated habitats, particularly marsh and seagrass, have long been known as nurseries for blue crabs," says Ralph, "with many previous field and lab studies showing higher density, survival, or growth of juveniles in seagrass habitats compared to un-vegetated areas nearby."

"Our study," she adds, "is one of the few to address the role of habitat complexity within seagrass beds, and the first to show on a broad scale that-all else held equal-denser, higher-quality grass beds hold more juvenile crabs."

Ralph says that on average, "there were 30% more crabs for every 10% increase in the percentage of seagrass cover within a bed during 2007, and 14% more crabs for each 10% increase in seagrass coverage in 2008."

Ralph says the team's findings are important because they "suggest that the quality of seagrass habitat can influence the population dynamics of blue crabs on a baywide basis." That raises concern given the historical decline in eelgrass-the Bay's main seagrass species-and projections of the continued decline of this cool-water species as water temperatures rise during the coming decades due to climate change.

"The potential for a future disappearance of eelgrass from the Bay is quite disconcerting given that the blue crab fishery was declared a federal disaster in 2008 and only recently recovered due to management actions by the Virginia Marine Resources Commission and other agencies in the Bay," says Lipcius. Tempering the team's concern are studies suggesting that blue crabs may also be able to use other, more heat-tolerant species like widgeon grass for nursery habitat as the Bay warms.

The team conducted the fieldwork for their study between 2007 and 2008, recording blue crab numbers and the percentage of seagrass coverage at 104 randomly selected sites along the eastern and western shores of the lower Bay.

Team members caution that their study was conducted at a time when historically low numbers of juvenile blue crabs were entering the population each year, likely due to overfishing and environmental factors. That might help explain one of the study's more unexpected results: contrary to basic ecological theory, the observed increase in the number of crabs did not level off as seagrass coverage approached the highest levels.

"The crab's lack of a threshold response to vegetation cover could have been caused by low densities of juveniles overall," says co-author Lipcius. "We'd like to repeat our study during a period of high recruitment to test the generality of the findings."

The good news is that they may be able to do that fairly soon, given the growing number of adult females in the Bay since 2008 in response to the fisheries management framework established that year. Each adult female spawns an average of three million new crabs each brood, and releases about three broods per year.

August issue of Marine Ecology Progress Series.

.


Related Links
Virginia Institute of Marine Science
Water News - Science, Technology and Politics






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





WATER WORLD
Earth's wobble "fixes" dinner for marine organisms
Princeton NJ (SPX) Sep 18, 2013
The cyclic wobble of the Earth on its axis controls the production of a nutrient essential to the health of the ocean, according to a new study in the journal Nature. The discovery of factors that control this nutrient, known as "fixed" nitrogen, gives researchers insight into how the ocean regulates its own life-support system, which in turn affects the Earth's climate and the size of marine fi ... read more


WATER WORLD
Obama urges new gun laws, swift Congress action unlikely

US military missed 'red flags' about gunman: Hagel

Flooded Acapulco hit by looting as tourists airlifted

New Technology can Detect Heartbeats in Rubble

WATER WORLD
Yahoo Japan develops 3D search engine-printer

GPS 3 And OCX Satellite Launch and Early Orbit Operations Successfully Demonstrated

'Terminator' polymer that regenerates itself

Northrop Grumman Delivers AEHF Flight 4 Antenna Precision Pointing Unit

WATER WORLD
Wetlands more cost-effective in nutrient removal, but multiple payments would be of uncertain value

Movement of marine life follows speed and direction of climate change

Water supply a problem for New Delhi's poor

Research shows denser seagrass beds hold more baby blue crabs

WATER WORLD
Warm Ocean Rapidly Melting Antarctic Ice Shelf from Below

Russia arrests Greenpeace Arctic activists, fires warning shots

Gas flaring and household stoves speed Arctic thaw

Russia to restore Soviet-era naval base in Arctic: Putin

WATER WORLD
The real reason to worry about bees

Study recommends strategies for improved management of fresh market spinach

Flame cultivation promising as weed control method for cranberry

New weapons on the way to battle wicked weeds

WATER WORLD
New storms loom as tourists seek Acapulco exit

Colorado floods death toll revised down

Airlift launched for tourists in flooded Acapulco

Death toll from Colorado floods rises to eight

WATER WORLD
160 UN peacekeepers desert Mali posts: military

Three Ivorian police killed in attacks

Uganda suspends 24 officers over Somalia corruption

Mali ministers met by hail of stones in Tuareg stronghold

WATER WORLD
Findings in Middle East suggest early human routes into Europe

Paleorivers across Sahara may have supported ancient human migration routes

Orangutans plan their future route and communicate it to others

New evidence that orangutans and gorillas can match images based on biological categories




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement