Archive for the ‘Marine Science’ Category

Getting to the Heart of the Matter

Wednesday, February 11th, 2015

On Valentine’s Day there is no escaping the hearts. They are on cards, decorating store windows, in emails, and so on. What better way to show our love of sea turtles than discussing sea turtle anatomy and physiology – in particular the heart.

Sea turtles, like most reptiles, have three-chambered hearts: two atria and one ventricle with a sinus venosus preceding the atria. Humans also have a sinus venosus, but only in early development – later it’s incorporated into the right atrium wall. The ventricle is comprised of three different parts:  cavum venosum, cavum arteriosum, and cavum pulmonae.

Clearly, there is a lot going on in the heart of a turtle, and while those scientific words may sound confusing, the way they work together produces incredible results. A UNCW researcher, Dr. Southwood, along with others conducted studies on heart rates and diving behavior of leatherbacks -the deepest divers of the sea turtle clan. Using an ECG she measured their cardiac activity while at the surface, while descending or ascending, and while at depth. Once the leatherbacks initiated a dive, their heart rate would immediately decline as they submerged. The rate would continue to slow and even reached as few as 1 beat per minute, indicated a physiological response to energy conservation.

These cardiovascular alterations indicate a species well adapted to time at sea, especially long periods of time under the waves. This is one more reason (as if we needed another) to appreciate those amazing creatures.

Understanding the Mysteries of Loggerhead Migration

Wednesday, February 4th, 2015

For centuries humans have been trying to navigate the oceans. Early attempts by the Phoenicians relied on celestial navigation over 4,000 years ago, and as ship design advanced, so did the navigational materials from early compasses, sextants, and astrolabes to modern-day radar, sonar, and GPS. While humans have been striving for a more efficient way to plot a course through the global oceans, one of our tetrapod friends has been doing this successfully, long before ancient or modern technology evolved.

We have long know that sea turtles have some kind of mapping system allowing them to travel long distances, yet return to natal beaches. Hatchling loggerhead sea turtles take a transoceanic trip, swimming from nesting beaches to the subtropical Sargasso Sea. They remain in this subtropical gyre for several years to mature, and then return back to beaches to nest. Over the years we were able to discern that they can interpret magnetic cues to determine their latitudinal position, but that is only half the picture. How were they able to orient themselves along the east-west longitudinal gradients?

In a new article from Current Biology, researchers from Chapel Hill have now provided that answer. Loggerhead sea turtles apparently use a bi-coordinate map with magnetic cues providing both latitudinal AND longitudinal information. Using a large water pool with a magnetic control field, the researchers would alter the magnetic field to mimic either a Puerto Rican orientation or a Cape Verde Island orientation. By using these two locations on opposite sides of the Atlantic, they were testing to see if sea turtles would swim in the proper direction to reach the Sargasso Sea. And it seems they did: turtles with the Puerto Rican magnetic field swam northeast and turtles with the Cape Verde Island field swam southwest.

It is remarkable to think that the hatchlings popping out of nests along our coast have an advanced navigation system in their tiny bodies. It is an innate ability, not something that they learn from migratory experience. Reaching the Sargasso Sea is an extremely difficult endeavor as they have to avoid both natural and manmade threat, but it is comforting that there is something guiding them along this journey.

Fish for the Future

Wednesday, January 21st, 2015

As fish stocks around the globe dwindle, people are turning to aquaculture to provide suitable protein resources. Aquaculture, in some form, has been around for thousands of years used by ancient Chinese, aboriginal Australians, and Polynesians on the Hawaiian Islands.  While traditional methods still exist, increasing use a technology, hormones, and other chemicals can pose harm to local habitats and requires some level of monitoring.

The National Oceanic and Atmospheric Administration (NOAA) has released a new Aquaculture Program with several priority areas including: science and research, regulation and policy, international activities, and outreach /education.  The overriding objective is to establish a strong, effective set of rules for marine aquaculture within the U.S. For years, we have trailed behind in the aquaculture industry, and with this initiative NOAA hopes to make the U.S. a world leader.

Currently the United States consumes almost 5 billion pounds of seafood annually; this includes shellfish as well as finfish. Globally, almost 50% of all consumption comes from aquaculture. Despite this high percentage, only about 5% of U.S. consumption comes from domestic aquaculture sources. Currently, we import about 84% of our seafood. This indicates areas open to considerable amount of growth in our own country, but requires guidelines to ensure that our coastal environments remain unaffected.

Some of the initiatives target alternative food development and stock assessment. Both of these areas could help the flagging fisheries, but also have the potential to cause deleterious effects to the local ecosystem without proper management. Currently the NOAA Aquaculture Program is open for public comment, click here to view the document.

Who are you calling a shrimp?

Wednesday, January 21st, 2015

Life in the ocean can be tough – especially when you’re a shrimp. Not only are you tiny and tasty, but new research shows that competition between shrimp is often violent and brutal.

The Indo-Pacific and Red Sea host several cleaner shrimp that are known for their symbiotic relationship with fish. In return for a meal, the shrimp crawl over the fish removing dead skin and parasites. While the shrimp maintain a cordial relationship with their clients, they can be openly hostile towards members of their own species.

Cleaner shrimp usually live in monogamous pairs, but the battle to get down to 2 individuals can be quite fierce. Researchers recently tested the shrimp’s competitive nature and found that when more than 2 shrimp were in a tank, they would attack and kill until only a pair remained.

Shrimp, like most crustaceans, are at their most vulnerable right after they molt. The savvy competitor knows that this is the best time to strike the fatal blow to their opponent. It should come as no surprise then, that researchers found that when shrimp were kept in groups they would delay the molting process as long as possible. Whoever shed first was usually the first to go. However, once a harmonious pair was established, they would return to routine molting.

The most likely reason for this behavior is played out across the animal kingdom – competition for scarce resources. Food is a limiting factor in the ocean, and shrimp want to make sure that they have guaranteed access to it. This will also result in an increase in body size, and a corresponding increase in the number of eggs laid. Regardless of motivation, it is clearly a “shrimp eat shrimp” ocean out there.

Will JAWS fears become a thing of the past?

Wednesday, January 14th, 2015

While sharks occasionally take nips at our sea turtle friends, we don’t hold it against them. The oceans are big places, prey maybe hard to come by and as oceanic predators they’re only obeying their animal instincts. They also occupy an important role as apex predators, and can serve as an indication of overall ocean health.

That is why a recent study published in Biology Letters causes pause for concern. Researchers from UC Davis and Stanford University have been conducting population estimates of great whites in the northeast Pacific. Their preliminary results surprised even themselves, “It’s lower than we expected, and also substantially smaller than populations of other large marine predators, such as killer whales and polar bears,” says the study’s lead author Taylor Chapple.

Using a seal-shaped decoy, researchers were able to photo ID individual species by their trademark dorsal fins. The jagged edges along the margins are unique, like fingerprints. Using this technique, researchers estimate that the region has 219 adult and sub-adult great whites. A sub adult is classified as having reached 8-9 feet in length and having shifted their diet from primarily fish to primarily marine mammals. An adult is a shark that has reached sexual maturity, which typically happens at 13 feet (in males) or 15 feet (in females).

The North American West Coast is one of three known white shark populations, the others being Australia/New Zealand and South Africa, and it is the location with the best population estimates. While numbers are lower than expected, further studies are needed to determine whether this is a population that is healthy or on the verge of collapse. Large pelagic fish species like tuna and billfish are in decline due to overfishing, and is conceivable that the great whites are suffering a similar fate.

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