Thursday, July 24, 2014

Dolphins in the coastal Everglades




By Postdoctoral Scientist Dr. Jeremy Kiszka
As the humidity returns, the thermometer rises and the afternoon thunderstorms water south Florida, we are reminded that the dry season has come to an end.  Over the months that spanned the dry season, however, our lab has been investigating dolphins in the Florida Coastal Everglades and associated areas of Florida Bay to answer questions about their behavior, movements and diets. 
We have been keeping a particularly close eye on the dolphins in the waters of the Shark River, Tarpon Bay, Oyster Bay, Joe River, and a 200 km2 stretch of coastal waters spanning east from Cape Sable to the Buttonwood Keys.  In May, three surveys have were conducted to increase sample sizes in Shark River and in Florida Bay, that will allow us to better understand the foraging ecology and ecological roles of dolphins in these areas.  With the 12 new biopsy samples collected we are up to about 35 samples and various analyses are underway, including stable isotopes to determine what and where dolphins are eating and persistent organic pollutants (e.g. PCBs, DDT) and Mercury (Hg). Preliminary results of stable isotope carbon and nitrogen analyses reveal that bottlenose dolphins feed in either coastal marine waters, as well as throughout river systems of the Everglades, from brackish to freshwater environments.
During our expeditions to the Everglades we have been able to observe some very interesting and unique behaviors of dolphins including strand feeding, mud ring feeding (solitary and in groups) and side swimming (in very shallow waters).  Biopsy samples taken from these animals may give us new information about diets specific to these feeding styles and behaviors. 

During mud ring feeding, a dolphin swims in a circle around a school of mullet while creating a ring of mud with its tail.  The mullet try to jump over the ring of mud and dolphins can catch them out of the air!




The nicks and cuts out of the dorsal fins help us identify individuals.

An osprey grabs a meal.



Some dolphins love to forage right next to - or even under - mangrove trees!

Thursday, January 30, 2014

Animal-borne video cameras reveal the secret lives of sea turtles


By Dr. Jordan Thomson, Postdoctoral Scientist

Like many aquatic species, sea turtles can be extremely difficult to observe in the wild so important aspects of their behavior remain poorly known. However, using new, high-definition animal-borne video cameras, we have gotten an astonishing look into the lives of these charismatic yet elusive creatures.

Motivated by a lack of understanding of the basic biology of endangered sea turtles, we used custom-built animal-borne video cameras to study the behavior of green and loggerhead turtles in Shark Bay, Western Australia. The researchers conducted over 120 camera deployments, yielding nearly 400 hours of video footage and an unprecedentedly detailed, first-hand view of turtle foraging patterns, diets, habitat use and social interactions – information vital to effective conservation.

The first peer-reviewed article to emerge from this research, published in the Journal of Experimental Marine Biology and Ecology, reveals strong patterns in turtle behavior associated with seasonal water temperatures (which have long been suspected but have proven difficult to observe). During summer, turtles in Shark Bay were highly active, spending most of their time exploring vast seagrass meadows, feeding, interacting with other turtles and keeping themselves clear of barnacles and algae by rubbing on rocks and corals (see article for video clips). When temperatures dipped in winter, however, turtles’ lives slowed to a crawl as they spent most of their time resting on the seabed and rarely came up to the surface to breathe.

While video analysis is ongoing, several other tidbits and video clips (Green Turtle Video 1) have emerged from this research. For example, green turtles in Shark Bay have a very broad diet consisting of seagrasses, algae, jellyfish and other invertebrates (unlike green turtles in the Caribbean Sea, for example, which eat mostly seagrass) (Green turtle eats seagrass, Video 2; Green turtle eats more seagrass; Video 3; Green turtle eats a sponge, Video 4). Loggerhead turtles feed on hard-shelled invertebrates and appear to be quite fond of blue swimmer crabs – but apparently need some practice at catching them (Loggerhead Turtle, Video 5). Limited rocky habitat in Shark Bay appears to be in high demand for resting and rubbing by green turtles, and sometimes things can get testy (Green turtle fight Video 6). And then there’s this clip of a tagged female loggerhead turtle spurning the advances of an interested male (Video 7) (who eventually decides to give up and try another day).

A valuable and evolving research tool, animal-borne video cameras continue to provide unique glimpses into the lives of poorly understood, and often imperiled, marine wildlife.  Check back later for more on our turtle-cams and the other species we are working on!  For now check out this video of a green turtle swimming past a cow tail stingray.

Additional Links

A trip to the Red Sea, Rabigh Lagoon

January 2014: Rabigh and Jeddah, Saudi Arabia

I traveled to the west coast of Saudi Arabia at the invitation of Dean Mohammed Al-Jahdali (a marine biologist) to start a collaboration between biologists at King Abdulaziz University – Rabigh Campus and FIU’s Marine Science Program.  We are working to develop a project to restore and study Rabigh Lagoon and the surrounding waters of the Red Sea.

After a long but pleasant couple of flights, I arrived in Jeddah in the middle of a sandstorm (luckily it was nice enough as we flew over the Red Sea on the Egyptian side to have a great view of the desert and coast).   

The Egyptian coast of the Red Sea.



It’s the first time I’ve been in a sandstorm, but I am told that they are very uncommon in this area! Needless to say with the high winds and flying sand I was a bit concerned about getting out on the water eventually!  The drive north from Jeddah to the small city of Rabigh lasted about an hour and a half and was through pretty much constant wind and sand. I am very glad I didn’t have to drive! 



The pictures just don't seem to show just how windy and
sandy it was!
































I spent the first day and a half talking to the scientists at KAU and touring their new campus and the city.  We had some amazing meals including fresh local seafood.  By the time we headed out to the lagoon I was really excited to see – and swim in – the Red Sea.   The trip was awesome.  We drove across hard-packed sand roads and encountered a large group of wild camels feeding along the shores of the lagoon early in the morning.  Once we left them, we drove along the shore of the lagoon and saw the roads that had blocked much of the flow of water from the lagoon to the Red Sea – forcing it through a single narrow pass until the government removed one of the roads just a few months ago.  Still, it looks like a couple of bridges to replace the roads with a couple pipes running through them would help the lagoon tremendously.



Road blocking natural flow to and from the lagoon

Pipes under the road don't let enough water through


Based on a quick look around, there is no question that the lagoon could use some restoration work.  Although the corals, seagrass and mangroves near the mouth of the lagoon that has always been open look pretty good, those farther away are not faring as well.  Still, there is a good amount of live coral and with the newly opened waterway, there is a good chance for restoration to make a big difference while Dean Mohammed works to have more flow restored to the bay.  
Heading out onto the lagoon

Seagrass in the lagoon covered by sediment


Coral and sponge inside the lagoon

Mangroves provide important nursery habitat for fish



Towards the end of our tour we had a chance to quickly poke the boat out to the reef that lies along the open coastline.  We just went a few hundred meters offshore to the reef crest and I jumpped in.  It took my breath away.  The amount of living coral, the colors, and the huge abundance of fish was maybe the best I have ever seen!  Of course, Dean Mohammed said it was like watching black and white TV compared to other areas down the coastline a ways.  I can’t imagine what that would be like!  Eventually, I was coaxed back into the boat to head back to campus to discuss the project.  I am pretty excited about the potential for a team to do an incredible marine restoration project as well as some amazing science in a beautiful area. 

The reefs outside the lagoon were covered in living corals and fish.






Tuesday, December 3, 2013

Dr. Adam Barnett's visit and sevengill sharks

3 December 2013

A couple weeks ago, we had the pleasure of welcoming Dr. Adam Barnett to the lab for more than a week.  Adam has been doing some really interesting work on sevengill and tiger sharks, and hopefully we can get some projects going together soon!  He also has been working on a great website with lots of information.  Check it out at http://www.oceansiq.com!

I'll turn it over to him for a brief update of what he's been up to!




Among other projects, I have been working on sevengill sharks Notorynchus cepedianus in the temperate waters of south-east Australia and South Africa, and tiger sharks Galeocerdo cuvier in north-east Australia (see our research projects at oceansiq.com), effectively studying two important apex predators in the two differing systems. The sevengill shark work in Tasmania Australia has been quite comprehensive, using a range of methods to show their habitat use patterns and the important role they play in coastal ecosystems. The study in South Africa has only recently begun and our focus site is False Bay, where we will also be identifying habitat use, the importance of the aggregation site in False Bay and the sevengill sharks’ role in the ecosystem. We will also examine if this role varies when they share the coastal system with white sharks Carcharodon carcharias. White sharks and sevengill sharks are widely distributed in temperate waters around the world, and these two co-occurring apex predators consume the same prey (e.g. fur seals and other sharks). Adult sevengill sharks (up to 3 metres in length) in coastal systems generally have little threat of predation, and any predation would be expected to come from the larger white sharks (up to 6 m). Despite this overlap in distribution and prey consumption, the relationship (if any) between these two apex predators is unknown. The work in South Africa will also provide the chance for cross regional comparisons in sevengill shark ecology.

To date, our tiger shark work has focused on the movement patterns of this species at Raine Island, the largest green turtle nesting site in the world. 


     A diver coming face to face with a sevengill shark at the aggregation site in False Bay, South Africa (photo credit Morne Hardenberg)

Taking blood from a sevengill alongside the boat (Photo Alison Kock)

Underwater view of sevengill restrained alongside boat (Photo Adrian Hewitt)