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Ocean Research

2015:  JAN | FEB | MARCH | APRIL

April 2015 Issue

Leatherback Turtles Navigate Via Magnetic/Solar Compass
The first analysis of migratory orientation in adult and subadult leatherback turtles has been published in Proceedings of the Royal Society B. The study found that leatherback turtles maintain remarkably consistent compass headings offshore, suggesting a common orientation cue or cues. Researchers speculate that leatherback turtles might use a magnetic and/or solar compass to find their way in open ocean.

The scientists fitted the animals with satellite time-depth recorders from August 2007 to September 2009 on their feeding grounds off Massachusetts. Fifteen turtles were tracked long enough to contribute data to the analyses, which were limited to track segments recorded in the western Atlantic subtropical gyre, part of a huge circle of ocean currents circulating from the equator to near Iceland and from the east coast of North America to Europe and Africa.

Currents within the gyre had little impact on the turtles’ trajectories. The leatherbacks traveled for an average of 32 days over distances of 686 to 1,372 miles while in the gyre.

Solar and magnetic features are ubiquitous and vary in a predictable way from north to south in this region, making them potentially useful for compass orientation. Individual leatherback headings were remarkably consistent throughout the subtropical gyre, with turtles significantly oriented to the south-southeast. Adult leatherbacks of both sexes maintained similar mean headings and showed greater orientation precision overall. The consistent headings maintained by adult and subadult leatherbacks within the gyre suggest use of a common compass sense.

Storms Help Spread Invasive Species
Researchers at Nova Southeastern University’s (NSU) Oceanographic Center have discovered that storms have a dramatic effect on ocean currents, which helps spread marine invasive species throughout a region. More specifically, NSU researchers looked at the distribution of lionfish in the Florida Straits.

“Lionfish are pretty sedentary, so this is like creating express lanes on a superhighway,” said Dr. Matthew Johnston of NSU.

The research focused on the explosion of lionfish populations in area waters, with findings published in Global Change Biology. The researchers found that as a hurricane passes, the flow of water shifts from a strong, northern flow to a strong, eastern flow. These changes in flow direction and speed likely carry lionfish larvae and eggs from Florida to the Bahamas and can explain how lionfish were able to cross the Gulf Stream so soon after their introduction to South Florida waters.

Once they were established in the Bahamas, hurricanes allowed lionfish to spread quickly against the normal northwestern direction of water flow in the area. The storms helped increase the spread of lionfish by approximately 45 percent and their population size by 15 percent. The larger implication is that global climate change, by causing an increase in storm frequency and/or intensity, could further accelerate the spread of marine invasives.

Navigation Course Now Free Online for High-Schoolers
The National Sailing Hall of Fame’s STEM Sailing program’s “Navigation on Land and at Sea” Course, which has been successfully delivered to 10th grade high-school students for the past three years, is now available online for teachers to use at no charge. There are eight lessons in the course, each designed to be delivered in a typical high-school class period.

Each lesson includes a PowerPoint presentation and lesson plan. There are also handouts to download and print for students, including worksheets and exams.

The course begins with a history of charts and maps, establishing their importance in both history and daily life. It progresses to teach students how to read, decode and decipher nautical charts and topographic maps, how to use a compass, conduct bearing triangulations, use dead reckoning to determine course and speed, and plot a course. The course also discusses the science of how a magnetic compass works, compass variations and True North, as well as how GPS works.

The “Science of Sailing” Course will also be available online.

Impact of Ocean Acidification On California Rockfish
University of California, Santa Barbara’s Gretchen Hofmann is one of seven recipients of a California Sea Grant Core Award from NOAA. Hofmann’s research focuses on the impact of ocean acidification on the early life stages of cabezon (Scorpaenichthys marmoratus), a bottom-dwelling rockfish in California’s coastal kelp forests. Cabezon are fished for food in the Santa Barbara Channel.

To date, no studies in California examine the vulnerable early life stages of this highly prized fish. By studying how acidic conditions impact their early development, the researchers can predict how the community as a whole will be impacted in the future.

Scientists expect that coastal regions such as the California Current Large Marine Ecosystem will be highly vulnerable to ocean acidification in the future as the resident animal and plant life within kelp forests face an environment with inadequate oxygen and low pH. Hofmann’s project will examine the organism-environment interactions of cabezon eggs and larvae and their relationship to levels of CO2 in the blood, as well as oxygen levels and temperature in the kelp forest habitat.

The pH of the water is directly related to the amount of CO2 in it, and the higher the CO2, the lower the pH.

The sensors will document conditions within the kelp at a Santa Barbara Coastal Long-Term Ecological Research Project site at Mohawk Reef and at Arroyo Quemado. Egg masses will be collected to rear in the laboratory under varied parameters based on sensor measurements.

Growth, energy usage, oxygen consumption, temperature tolerance and survival capability of cabezon eggs will be tracked. Also under study will be whether the genetic makeup of certain cabezon makes them more resistant to pH change.

2015:  JAN | FEB | MARCH | APRIL

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