World Seagrass Month

Happy World Seagrass Month!

Seagrass is an underwater, flowering plant that can be found in relatively protected and healthy bays, with 60 species worldwide. Seagrass meadows are a critical habitat for young finfish and crustaceans, help protect our coastlines from storms and rising tides, and also soak up nutrients and bacteria, helping to keep our seawater clean. Two species of seagrass are found in Massachusetts: eelgrass and widgeon grass.

 But seagrasses around the world are being lost at a rate of about two football fields every hour. Many things can damage seagrass, from polluted water to boats dragging their anchors. To track changes in eelgrass, Mass DMF conducts diver-based and remote-sensing eelgrass surveys in bays throughout our coast and participates in SeagrassNet, an international seagrass monitoring network.

 In addition to successfully restoring tens of acres of eelgrass in Boston Harbor and Salem Sound, the team collaborates with partners on interesting projects like genetic diversity, citizen science monitoring, wasting disease, invasive species, and conservation moorings. DMF provides expertise and leadership in issues pertaining to seagrass and other sensitive habitats through the Technical Review process.

Keep tuning in to the blog to learn more about the exciting seagrass projects DMF has planned in 2018, and HAPPY SEAGRASS MONTH!

Expanded Eelgrass Meadows in Swampscott

On August 23, 2017 the Massachusetts Division of Marine Fisheries (MA DMF) Habitat Team set out for Swampscott Harbor in search of eelgrass. Armed with a Humminbird acoustic sonar transducer, an underwater video camera, and the DEP 2012 aerial photo-interpretation eelgrass maps, we anticipated finding a bed similar to the size and footprint of the Swampscott Harbor mooring field, where DEP previously mapped a 23 acres meadow.

We were happy to find that not only has the Swampscott bed expanded to a total of 153 acres (a 665% expansion from DEP's 2012 mapping), an adjacent bed exists to the east of Swampscott Harbor which had not previously been mapped. This "new" bed is approximately 36 acres in size and is located in the cove east of Lincoln House Point.  While it is very close to the Swampscott Harbor bed, we believe that they are actually separate beds and not connected (see map). The eelgrass appears to be dense and healthy, and the sediment sandy. Reproductive shoots, some epiphytes, colonial tunicates, snail grazing, algae and potentially wasting disease could also be seen in the groundtruthing images (photos below). We found a somewhat uncommon algae, which we believe to be a Cord Weed (Chorda sp.), growing near and further seaward of the eelgrass meadow. It has a more similar appearance to eelgrass than most algae do (photo 4), however it did not share the same characteristic appearance in the sonar data so we are confident it was not mistakenly mapped during this survey.

Despite the good health and expansion of the bed in Swampscott Harbor, several human created impacts were observed in the sonar images.  The large pier and several dozen moorings in the harbor create scars and bare areas within the bed where pilings have been placed or  mooring chain has dragged on the bottom.  Too many direct impacts such as these could contribute to the bed becoming stressed or fracturing and shrinking in overall size. Impacts can be reduced by using specially made conservation moorings designed to reduce scars and by reducing/limiting the number of new and existing moorings located within the eelgrass bed.

By using side-scan sonar imaging to map eelgrass, we are able to quickly and effectively locate the extent of beds including areas unable to be confirmed by aerial imagery alone. An underwater video camera is used to groundtruth the sonar data.  We believe that continued use of sonar imaging will allow us to keep discovering new and/or expanded eelgrass beds in Massachusetts, as well as keep close records of how mapped eelgrass beds fluctuate over time.

Aerial photos reveal boat mooring impacts to seagrass meadows in West Falmouth Harbor

This week I enjoyed a breathtaking flight over Buzzards Bay thanks to a LightHawk donated flight http://lighthawk.org/ flown by pilot David Murphy.  I was focused on West Falmouth Harbor to take aerial photos of the impact of boat moorings on seagrass meadows, as part of a project funded by the Atlantic Coastal Fish Habitat Partnership.  The photos below show the striking mooring scars in the eelgrass bed.  Propeller and rudder scars are also evident. 

MarineFisheries received a grant in 2012 from the Atlantic Coastal Fish Habitat Partnership to continue studying the impact of conventional moorings (anchor and chain) on seagrass meadows, and to test the utility of a new innovative mooring design referred to here as a "conservation mooring".  Previously, we tested conservation moorings installed in Manchester-by-the-Sea and we continue to monitor the mooring scars and measure changes at that location.  The new funding enables us to expand the project to a harbor on the Cape and test the concept in a different system.

Conventional moorings have heavy chain that drags along the bottom, stirring up sediment and ripping out seagrass.  Conservation moorings use floating, flexible line that does not contact the bottom and a helical anchor driven into the sediment for maximum holding power with minimal footprint.  These systems may minimize scouring of the seafloor and reduce impacts to seagrass and water quality. 

A) Conventional Mooring with chain drag; B) Conservation mooring and eelgrass

Left: helical anchor; Middle: Hazelett flex rode; Right: Ecomoorings flex rode

Dave Merrill installing a helix mooring anchor in W. Falmouth

With grant funding, 8 conventional moorings were voluntarily converted at no cost to the owner, to a conservation mooring.  Such conservation moorings have been in use locally for several years already in Marion, Chatham, Tisbury (Vineyard Haven), and Lake Tashmoo, with good reviews from boat owners and harbormasters.  There are several designs and brands of conservation mooring.  Eco-Mooring by BoatMoorings.com, a New England based company, and Hazelett Systems, were chosen for comparison in West Falmouth Harbor.  Dave Merrill of BoatMoorings.com worked together with the local mooring maintainers in West Falmouth to install all 8 moorings in May 2013.

These photos will be our "before" conditions.  Stay tuned in the coming years to see how this seagrass meadow changes.

Declining density and extent of eelgrass at Salem Sound and Nahant could be due to storm damage

Hi! Back in the water again after a long winter in the office...

Nahant

So far we have been to the Nahant meadow twice this spring.  The first time in April we came to retrieve a hobo temp/light monitor and harvest for plantings in Boston Harbor outer islands. Notes from August 2012 at that site indicate that plants were tall and lush, 75% cover and approximately 80shts/m2 with many reproductive shoots.  The meadow was continuous with few open patches.  But in April, we observed a low density patchy bed with large eroded areas and other areas of deep sand waves.  Our screw anchor, installed back at the end of August 2012, was buried up to the eye. 

We were back at the Nahant eelgrass meadow last week looking for a site to establish a monitoring station.  We ran a drop camera along several transects spaced throughout the DEP mapped area.  We were surprised and disappointed to find a large portion of the area mapped by DEP in 2006 is now gone and the remaining grass is mostly patchy, similar to what we saw in April.  The southeast lobe of the bed persists, but has contracted from it's 2006 extent.  Check out the rough map below digitized from our field notes, showing the remaining meadow, and an area of patchy grass and other sections of the bed that are now only sand waves.

We plan to return with divers for a closer look to help determine what might have occurred.  From the camera view it appeared that sand waves had swept over the bed, possibly burying the grass.  This meadow has long been a lush dense meadow and one of the few remaining north of Boston of this size (in MA).  Many groups have used this bed as a reference bed and donor bed for eelgrass projects in Boston.  The green dots on the map above show the locations where we are investigating possible establishment of a new SeagrassNet, long term monitoring station.

Salem Sound

At our SeagrassNet site in Salem Sound (Misery Island, Beverly) we also found low density and evidence of erosion.  It looked like much of the sand had been washed away leaving a hard-packed clay.  There is still grass clinging to the clay, so hopefully as the season progresses it will fill back in.  I think we are seeing the effects of a late winter with several storms, including NEMO in February 2013.

Sand eroded away leaving hard-packed clay over much of the shallow side (transect A) of the meadow

SeagrassNet quadrat showing low density eelgrass and eroded areas of clay

erosion around a small eelgrass clump near transect A

Taking a biomass sample on Transect B

Mooring video, Salem Sound Under Water lecture series and more!

Greetings from the MarineFisheries eelgrass team!  Like many of you, much of our winter work involves crunching data from the previous field season and disseminating our findings in reports and public presentations. I recently gave a presentation as part of the “ Salem Sound Underwater” lecture series hosted by Salem Sound Coastwatch (http://www.salemsound.org/) The talk focused on eelgrass, why it is important and what we are doing to map, monitor and restore it to our coast. 

 The next presentation in the series will be "Saltmarshes Under Siege" by Robert Buchsbaum of the Mass Audubon Society,  March 27th, 7pm at the Marblehead Abbot Public Library.

We are always trying to find new ways to engage the public through presentations, pictures and videos.  Recently, we edited some of our field work videos to turn them into educational tools.  One example is our video of a dive on a traditional, block and chain, boat mooring. The footage, captured in July 2011, demonstrates divers monitoring a boat mooring located within a mooring field that overlaps an eelgrass meadow in Manchester-by-the-Sea. The chain from the traditional mooring system drags along the bottom, scouring the seafloor as it sweeps in and out with the waves. This was not a very windy day, but look at that chain bounce!

The Manchester mooring project was part of a collaboration with the Mass Bays Program and was funded by the Association of National Estuary Programs with a NOAA Community Based Restoration Partnership Grant.  The primary objective of the project was to restore eelgrass to denuded areas around traditional block and chain mooring systems.  Sixteen block and chain moorings were replaced with conservation mooring systems in existing eelgrass beds: eight in Manchester and eight in Provincetown.  Following replacement of the moorings, eelgrass was transplanted into a subset of the scars to determine if transplanting would facilitate the recovery of eelgrass.  Monitoring has been performed annually and is still underway.  For more information, refer to the project poster here: http://www.mass.gov/dfwele/dmf/programsandprojects/neers_mooring_poster.pdf

Looking forward to Spring and our upcoming field season!

- Tay Evans, MarineFisheries biologist