Invasive Species From the Depths: submersible can prove to be method of transport

From time to time, I will bring up the issue of invasive species, most recently in April regarding the armored catfish.  The transference of a species from one ecosystem to another can cover great distances, such as with the lionfish of the Pacific but now growing in numbers in the Caribbean.  Everything from animal larvae to seaweed can be transported via freighters either by attaching to the hull or inside the bilge.
       
Nature can use various mechanisms to keep some species within specific territories; distance, temperature, predators, and the end results of years of evolution that can involve a variety of minute but important factors.  And in some cases there is the natural boundaries established by depth.
             
While ships, planes, automobiles, and even the careless aquarist can be methods of transportation for shallow water of coastal species, plants and animals at depth have a natural barrier to help keep species in place.  But it's not always the case, as was recently discovered with the world-famous submersible, Alvin.
            
As reported in the Conservation Biology journal, Alvin had been conducting deep sea missions around thermal vents in the Pacific when 38 small limpets were discovered attached to the submersible.  Researchers examined the small invertebrates and were dismayed to find that they were actually a species from a different deep sea area of the Pacific, nearly 400 miles away, where Alvin had been previously.
              
The greatest concern with the discovery was the fact that this particular species of limpet, Lepetodrilus gordensis, carries a parasite in as much as 90 percent of the population.  Transferring this animal to other pristine deep sea environments could have disastrous implications.  The researchers were a bit surprised to discover that the limpet had withstood the change of pressure from the deep depths to the surface.
              
Alvin, owned and operated by the Woods Hole Oceanographic Institution, is typically cleaned after every dive, particularly around the equipment used to capture specimens.  Sloppiness is definitely not part of the Woods Hole regimen, so addressing how these limpets managed to slip by is critical.  Discussions are being held to consider more thorough cleaning procedures, including the use of fresh water, which can kill most salt water organisms.
                
Deep water ecosystems, thousands of feet below the surface, are very isolated ecosystems, protected by depth and pressure, and therefore the consequences of introducing new species could be very disruptive.  Researchers can not necessarily guarantee that there will be adverse effects, but it is certainly something that they would prefer not to have to deal with.
                              
"We know from shallow water systems that one mistake can completely change a system," said Dr. Amanda Bates from the University of Tasmania and one of the researchers involved.  "The scientists themselves have to be better at not getting caught up in their research, just taking a step back and making sure that those jobs are getting done."  
                  
Source: Discover Magazine
Source: The Australian          

How Do You Clean A Shark's Skin?: small reef fish know how

Sharks have amazing skin - sleek and smooth when felt in one direction, as rough as sandpaper when felt in another. Shark skin is built on denticles, rather than scales, which is similar to the compounds that also make up the predator's teeth. In many species of pelagic, or open ocean, sharks, the skin is tightly woven and very hydrodynamic, making it impervious to many but not all of the ocean parasites that are floating about looking for a host and a free ride.

For those persistent parasites, like copepods, which are able to latch onto a passing shark, some sharks, according to researchers at Bangor University, North Wales, U.K., will make use of one of nature's symbiotic relationships that is also utilized by many reef fish to rid themselves of annoying parasites.

In reef communities, from tropical to cold water, there are small fish that will remove parasites and other material from the skin of larger fish. By doing so, the smaller fish is provided a food source and the larger fish receives a hygienic cleaning. Symbiosis evolves because the larger fish, which could easily consume the smaller fish, realizes the benefit from the smaller fish's actions and allows the cleaning fish to go about its business, even swimming into the larger fish's mouth and through its gills to provide a thorough cleaning.

Having studied several species of sharks in the Philippines, Bangor University researcher Simon Oliver says that several sharks, like the endangered thresher shark, will sometimes move into coastal areas not to feed but for the express purpose of getting a parasite-removal cleaning.

"Parasites are extraordinarily successful organisms and would propagate if the sharks had no way of getting rid of them. So these cleaning services are essential to the life history of these animals," said Oliver.

In tropical environments, the cleaner wrasse, or bluestreak wrasse, is known for staying in one area, establishing a "cleaning station" where large fish will hover patiently while the cleaner wrasse goes about its work - an oceanic car wash of a sort. In colder climates, fish like the senorita, another type of small wrasse, perform the same function. Oliver suspects that, while not all species of shark are able to literally stop and hover while getting a grooming, he did see evidence of sharks coming in close and getting a beneficial once-over by resident cleaner fish.

Oliver also observed that the sharks would momentarily set aside the tendency of some species to resist close contact with other species of sharks.

"It's like a lion at a waterhole with an antelope. Its thirst takes precedence over the natural order of things. The grey reef shark could easily take a bite out of a thresher, or a ray, but doesn't, which shows the necessity for these cleaners" said Oliver.

Not all sharks will swim to sea mountains or coastal reefs to take part in this kind of dermatological hygiene. Makos and white sharks can be observed with long, hair-like streamers along the edges of their fins - the telltale sign of established parasites. But it is another fascinating aspect of behavior in the ocean environment that even pelagic animals, like some species of shark, have come to recognize and take advantage of what the reef fish community has to offer other than being a source of prey.

Read more about shark cleaning in the BBC News.

And the meek (or microscopic) shall inherit the earth

Discussions of climate change often focus on the big events that can catch the attention of the public - hurricanes, fires and flooding, vast sea melts, etc. But what can be most alarming are the subtle, microscopic changes that can have enormous consequences.

I was reading the latest Marine Science Review available from Seaweb.org (No. 267 - Pathogens, disease, and die-offs). It covers everything from epizootic shell disease in lobsters to wasting disease in burrowing starfish, and much more. Many of these events are isolated or cyclical outbreaks, but increases in water temperature is becoming more and more of a potential factor.

Increases in water temperature - even very small changes - can produce two negative effects: an increase in bacteria and viral microorganisms, and a weakening of the immune system of many aquatic life forms. Will Nature adjust to these changes? Most likely, but at what cost to various species?

To borrow the Biblical phrase, the meek shall inherit the earth. But it may not be the banner-waving, peacenik; it may be something smaller than the head of a pin - meek but deadly. Another important aspect of climate change that has to be considered.