Marine Event of the Year - 2011 Tropical Storm Irene

Tropical Storm Irene hit New England on August 28th, 2011 with onshore winds on the east side of the storm battering coastal areas with large waves and a destructive storm surge.  After the storm, I traveled to Provincetown during calm weather and monitored the docks at Provincetown and Wellfleet on August 31st and September 1st.

Tropical Storm Irene Hits New England

 Tropical storm Irene over New England brought onshore easterly winds

 and turbulent waters to the Massachusetts coastline.  

 

Satellite view over the Northeastern US with outlines of the states superimposed. The image was taken when the eye of the storm was near New York City.

  Left, projected path of Hurricane Irene when it was in the Carribean.  Irene started its journey as a hurricane in Puerto Rico, made landfall over eastern North Carolina's Outer Banks, and was downgraded to a tropical storm as it passed over Long Island, NY.  Right, it continued through western New England battering CT and VT.  The threat level through the Northeast was extreme with widespread damaging winds through August 29th.

The storm had a significant effect on marine life on the sides of docks, scouring off loosely attached organisms and battering firmly attached species.  Most of the colonial species and algae that extended away from their attachment site were pruned or torn off and some species appeared bruised or damaged.  Firmly attached species like Styela clava and Codium fragile survived the storm, but filamentous and leafy algae were washed away or pruned shorter taking with them the species (e.g., amphipods) that grew on or among them. Outgrowths of Didemnum vexillum were torn off at the base, as were large colonies of Botryllus schlosseri and Botrylloides violaceus.  In Wellfleet, an almost solid covering of a spring cohort of Molgula sp.(manhattensis?) on portions of the seasonal docks was decimated resulting in large areas of the docks being cleared of the ascidian.

Monitoring at MacMillan Wharf, Provincetown, 2 Days after the Storm

Inspecting colonial organisms on August 31st using the palm of my hand to make a small pool of water and preparing to magnify the field with a jeweler's loupe. 

A month later, by the September monitoring visit, there was a clear re-colonization of the depleted areas in Provincetown by algae, ascidians, and other invertebrates.  Didemnum vexillum grew up the sides of the dock from established areas lower on the dock, and Diplosoma listerianum, not found at the beginning of the season, surged in its colonization from its first sighting in August.  Botryllus and Botrylloides repaired their torn edges and resumed their previous growth.  Near the water line, small individuals of Styela clava (under 1 or 2 inches) were scattered along the dock on newly exposed substrate.  In Wellfleet, there was no noticable re-colonization of cleared surfaces by Molgula, but Botryllus schlosseri growing on the remaining Molgula continued to grow and spread, and there was some regrowth of algae and other attached species along the water line. 

Striped Anemone at Wellfleet Marina

Wellfleet Harbor and Marina
                     

Wellfleet Harbor is located on the west side of the Cape Cod Peninsula (see satellite images of Cape Cod along sidebar at right) and is home to the renown Wellfleet oysters.  The town marina is located at the north end of the harbor and was built over a natural strip of land at the mouth of Duck Creek.  A long permanent dock is located on the north side of the marina that I monitored during the summer of 2011 (see satellite image and photo of the marina, below).  The dock rests on concrete covered polystyrene floats similar to those found in Provincetown.  Virtually all the boats moor rear-first at the dock, but there is a perpendicular, seasonal dock with wood sides near or at the end of the long dock for side boat-entry.  During the winter, I am told that the individual sections of the permanent dock are brought to the west end of the bay for protection against winter storms.

  

Wellfleet Marina North and South

The North Marina features permanent docks with concrete-covered floats for fishing and recreational boats.  The South Marina features the harbormaster seasonal docks and public docks that rest on modular floats composed of polyethylene plastic shells encasing polystyrene cores. 

Wellfleet Marina North Facing the Mouth of Duck Creek

Permanent docks at the mouth of Duck creek provided a substrate for settlement by Diadumene lineata. The water was turbid with sediment, ranged 70-80 degrees in temperature, and had a favorable bay salinity of 32 parts per thousand.

In comparison to the other bays studied, Wellfleet marina had a relative low diversity of species on its docks.  The dominant, year-around species was the common oyster, Crassostrea virginica which covered the intertidal rip rap and grew to mature size on the underside of the dock floats.  The sides of the permanent docks also had a few mussels and empty shells, but not a new cohort of young oysters.

The Wellfleet oyster industry dates back prior to the Revolutionary War.  In the 1700's, native oysters were harvested.  During the mid 1800's, young oysters were shipped in from Chesapeake Bay and grown to maturity in Wellfleet Bay.  During the late 1800 and 1900's, aquaculture techniques were developed, and today the bay is home to a thriving oyster industry that celebrates each fall with its Wellfleet OysterFest.  The shallow bay that is so favorable to oyster beds is also probably one of the features that make it a favorable environment for the orange-striped anemone, Diadumene lineata (also listed as Haliplanella lineata).   

Diadumene lineata - the orange striped anemone

                     

Diadumene lineata is a small anemone about 3 cm in diameter, with a smooth, brown or green-gray body, with or without vertical orange stripes.  The crown is topped with 50-100 slender, tapered, fully retractile tentacles that are transparent, pale yellow, beige, or light green.  It is native to northeastern Asia but has spread around the world to temperate climates in both the northern and southern hemispheres.  It is commonly found on pilings or floating docks of protected shallow waters such as harbors and is often associated with mussels or oysters.  It is extremely tolerant to extremes in temperature, salinity, and water quality.  This tolerance probably explains its distribution in Wellfleet in an area that is generally unpopulated by other attached and encrusting species. 

Diadumene lineata - Portrait by Underwater Photography

A view of Diadumene as seen in the literature. This image by R. Manuel is from A Guide to Invasive Marine Species of Hawaii by Eldredge and Smith, 2001. 

Within my monitoring areas in the Gulf of Maine, Wellfleet was the only site where we saw Diadumene, and within the Wellfleet Marina, it was most common along the long permanent dock in the north, protected bay.  The permanent docks of Wellfleet Marina are dominated by oysters, in contrast to Provincetown Marina or Salem Sound where the mussel Mytilus edulis is the common bivalve.  Diadumene is relatively inconspicuous to the eye but can been seen growing at moderate density in social groups on the vertical dock surfaces and on oyster shells.  

Diadumene lineata Growing on Oyster Shell

Individuals were photographed shortly after collection (9/1/2011).  Most individuals were fully open, but one is closed at the bottom center revealing the orange stripes. 

Under the stereomicroscope, Diadumene took on a new look.  The light colored tentacles had a luminescent glow, and with menthol anesthesia, the tentacles moved around in slow motion.   The anemones were partially immobilized, and the tentacles appeared shorter and more stout (compare the length of the tentacles of the anemones below to the ones in the photo above). Two color variants were seen, a majority with light yellow tentacles and a less frequent variant with light brown tentacles.

Diadumene lineata Growing on an Oyster Shell

                     

Diadumene lineata viewed with a stereomicroscope using fiber optic lighting.

The specimens were collected in July 2011 and anesthetized with menthol crystals.

The light colored tentacles had a luminescent glow.  2X zoom x 10X objective.

Diadumene lineata with Brown Translucent Tentacles

Diadumene lineata viewed from above showing the mouth and orange stripes.  This individual was also anesthetized with menthol crystals.  2X zoom x 10X objective.

Color Variants of Diadumene lineata

The two color variants of Diadumene lineata detached from the substrate

after menthol relaxation.  1.5X zoom x 10X objective.

View of the Mouth of Diadumene lineata

Beige colored mouth surrounded by rings of brown tentacles 

(above mouth, a small piece of adhering debris).  4X zoom x 10X objective.

Distribution of Diadumene in New England marinas (RI to Maine):

Pappal, A, Pederson, J, and Smith, JP.  Marine Invaders in the Northeast.  Rapid Assessment Survey of non-native and native marine species of floating dock communities. 7/25/2010 - 7/31/2010

Special thanks to Adrienne Pappal and Niels Hobbs for confirming the species identification of Diadumene from sterezoom micrographs.

Links providing further information on Diadumene lineata:

Guide to Marine Invaders in the Gulf of Maine

A Guide to the Exotic Species of San Francisco Bay

Introduced Marine Species of Hawaii

Actiniaria.com

Nemesis: National Exotic Marine and Estuarine Species Information System

WoRMS: World Register of Marine Species

WILD Singapore Fact Sheets 

References on the history of Wellfleet:

1.  Wright, D.B. The Famous Beds of Wellfleet.  A Shellfishing History.The Wellfleet Historical Society, 153 pp., 2009. 

2.  Lombard, D.  Wellfleet, A Cape Cod Village.  Arcadia Publishing, 128 pp., 2000.  

New Ascidian Images on Tunicarium

Botryllus schlosseri is another beautiful colonial ascidian whose single and multi-color variants make for an amazing number of color morphs.  These colorful ascidans, like Botrylloides violaceus (Nov. 11 Post), make for terrific underwater photographs that I thought would transcend directly to the stereomicroscope.  It did to an extent; however, like with Botrylloides, structural detail was easier to capture with the lighter color variants.  Some of the stereomicrographs from this summer's monitoring of Cape Cod and Salem Sound marinas are now featured on Tunicarium, including images of the invasive ascidians Botrylloides violaceus, Botryllus schlosseri, and Didemnum vexillum.  

Botryllus schlosseri was a challenging colonial to capture under fiber optic lighting. The variants with dark-colored zooids blended in with the backgrounds making difficult the photography of structural detail.  With the light color variants against a darker background, the two-toned beige, which formed a mosaic-patterned colony, and single-colored orange colonies proved to be highly photogenic.

To capture the zooids with open siphons, I tried Gretchen Lambert's technique for relaxation with menthol crystals.  It was terrific for relaxing ascidians as well as other invertebrates.  But as with any approach, I found relaxation had its pros and cons for viewing as well as photomicrography.  Relaxation greatly reduced contraction ability, but also inhibited the ability of zooids to fully expand. Lack of anesthesia was challenging under bright light because individual zooids reacted to the light independently, each zooid in a cluster randomly closing and re-opening during photography.  My objective was to obtain images where all the branchial siphons in the field of view were fully open.  It made for some interesting and entertaining time-sequence shots.    

The images below are two of my favorites.  They demonstrate the difference between the information revealed capturing images of light vs. dark Botryllus color variants and show zooid structural and pigment cell details that cannot be seen solely by underwater photography.  The 40X original magnification generated images with the greatest resolution and zooid detail (4X zoom + 10X objective lens).  These details can also be seen out in the field with the 30-40X jeweler's loupe magnifying glasses that I discussed in the Nov. 25 Post.  The beige variant gave vivid zooid detail, whereas the typical white star on dark purple was outstanding for showing cells in the pigment bands.

Botryllus schlosseri Beige-Rust Mosaic Variant

Botryllus schlosseri growing on the green algae Codium fragile collected from MacMillan Wharf, Provincetown, MA. Zooids have a translucent beige color revealing the tips of the branchial tentacles and pale rust-orange cells in the pigment bands. 

Botryllus schlosseri White Star Variant with Parallel Pigment Bands.

Botryllus schlosseri growing on Codium collected from MacMillan Wharf, Provincetown, MA.  Four branchial openings are seen at the top with 4 pairs of white pigment bands leading to the single, common atrial aperture at the bottom center.  

The full collection of images on Tunicarium can be seen all together on Google Images that has been web-searched using the word "Tunicarium".  The photos are featured in thumbnail view and can be "double-clicked" to see the jpg files saved on the website.  Larger sized micrographs can be obtained from me by request at tomermak@rcn.com.