Subscribe to Chronicles!

July 2014
« May    
Nature Blog Network

Tweet Blender

The Decline of Seagrass Meadows

Zostera! Eelgrass, Zostera marina, is a flowering, marine vascular plant that remains submerged all the time. This is quite a feat for vascular flowering plants, and only a few dozen species world wide are capable of growing completely submerged in a marine environment. Eelgrass creates and extremely important habitat, its upright structures and complex root system create a 3-D living space for many different types of animals. It is (or was) the dominant habitat forming SAV (submerged aquatic vegetation) throughout much of the coastal waters in the northeastern United States. Unfortunately, for various reasons, eelgrass meadows have seen drastic declines, and in many locations eelgrass only exists in a mosaic of small patches. This is extremely bad news as many of the important, and formerly important, commercial and recreational fisheries of the northeast US are dependent on Zostera at some part of their life cycle as a nursery and foraging ground. Some of the species are finfish like tautog, bluefish, fluke, winter flounder, porgies, while others are shellfish such as blue mussels, hard clams, oysters, bay scallops, and blue crabs. Many of the aforementioned species support or once supported vibrant fisheries. Many of those fisheries have collapsed, also for various reasons. However, is it possible there is a link between the crash of the fisheries, the decline of Zostera and the failure for recovery on both ends?

Bay Scallop on Eelgrass

Argopecten on Zostera! Bay Scallops, Argopecten irradians , have developed a very close relationship with eelgrass, Zostera marina. As larvae, they are passively transported, and tend to settle in eelgrass meadows when the current is dampened by the 3D structure of the seagrass. This same 3D structure provides post-set juvenile scallops a spatial refuge from predation. Even as larger juveniles and adults, scallops are capable of, and have been shown to, actively select eelgrass habitats.

Other species also use eelgrass

grass shrimp A number of other species utilize eelgrass as a habitat. Included are grass shrimp, like the Palaemonetes pugio, other decapods such as blue crabs, bivalves such as hard clams, gastropods (snails), and numerous fish species, including winter flounder, tautog and cod.

All’s not well in Oz…

A colleague, friend, and former roommate of mine took a post doc position over in Australia around this time last year, doing harmful algal research.  He recently sent me this video:

flooding in australia

It’s pretty wild.  And to think, people here on the east coast are complaining because their streets weren’t plowed fast enough! Imagine these rapidly moving flood waters racing down your street? Absolutely nuts.  It has claimed lives and caused considerable devastation.  Obviously, due to the harsh weather we have been receiving here, we haven’t heard all that much about the flooding.  You can read about some of it here, here, here, and here.  My friend Tim even blogged about it.  Google it too, theres plenty of info about it out there.

An interesting article I came across piqued my interest – the flooding has supposedly given bull sharks access to the town streets, and a couple have been spotted swimming around.   Could you imagine? I mean wow! I find that both exciting and petrifying.  On one hand, it just speaks to the incredible adaptive ability of bull sharks.  On the other hand, they are often considered among the most aggressive sharks in the world, and you wouldn’t expect to see them wading through floodwaters in the middle of you town.  Many of you are probably thinking how impossible that must be.  But bull sharks are tolerant of fresher waters, and in some parts of the world, are found venturing up rivers!  They are extremely tolerant of wide-ranging salinities via unique osmoregulation abilities.  In fact, these sharks are often found in rivers, even in the US, like Alabama and the Potomac River.   It is also thought that a bull shark is responsible for the Matawan creek attacks in 1916, an event originally attributed to a white shark and the inspiration for the movie Jaws.

Maybe Chuck over at Ya Like Dags or David over at Southern Fried Science might have some more insight into the reasons bull sharks are so freshwater tolerant.  But I thought it was interesting and worthy of mention.

Edit- Shark biologist Lyndell Bade informed me that bull sharks can be found up the Mississippi all the way to St Louis and can live in Lake Nicaragua.  These are quite amazing fish.

1 comment to All’s not well in Oz…

Leave a Reply




You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>