A few of the “critters” we saw during our last seagrass survey…
Moon jellyfish season is something we are used to dealing with here in the Florida Keys. The sting from a moon jelly is mild and they are actually quite beautiful to observe but, as jellyfish are one of the most feared organisms of our oceans, snorkeling with students at a reef with swarms of moon jellyfish is anything but a mild and beautiful experience. There is little we can do to prevent the students from screaming and thrashing as if a great white shark was barreling towards them with its jaws wide open. So, we patiently wait for the moon jelly season to end as they drift to another location. But this season, my patience is wearing thin. The swarms are only getting larger. I can’t help but wonder if the jellyfish invasion I have read about is actually happening before my eyes as I ignore it, simply reminding the students to stop screaming, keep their faces in the water and swim around them.
Over recent decades, man’s expanding influence on the oceans has begun to cause real change and there is reason to think that in some regions, new blooms of jellyfish are occurring in response to some of the cumulative effects of these impacts. The link between ocean degradation and jellyfish makes biological sense. Nutrient pollution can increase food supplies for jellyfish, overfishing can reduce their competition, and warmer temperatures are thought o trigger reproduction in some jellyfish species.
By the pulsed nature of their life cycles, gelatinous zooplankton come and go seasonally, giving rise in even the most undisturbed circumstances to summer blooms. Even holoplanktonic species like ctenophores increase in number in the spring or summer when planktonic food is available in greater abundance. Beyond that basic life cycle-driven seasonal change in numbers, several other kinds of events appear to be increasing the numbers of jellies present in some ecosystems. In 1996, Dr Graham of the University of Mississippi reported that from 1985 to 1997, moon jellies of the Gulf of Mexico had grown substantially more widespread and abundant. In the Bering Sea, one of a handful of locations with a monitoring record longer than a few years, jellyfish numbers had also risen through the 1990s.
However, some researchers in the Gulf and Bering Sea now believe that long term natural climate cycles have an important role in controlling populations there. Jelllyfish naturally form blooms. The challenge for researchers lies in separating normal fluctuations from those for which humans might deserve some of the blame.
A recent study (Graham 2012) suggests that as of right now there is not enough evidence to support a global upswing in jellyfish populations. A problem with jellyfish is that they are difficult to study so they have received little attention from marine biologists. We have little long term data. Typical nets shred them and many jellyfish have complex life cycles. Several species, including moon jellyfish, reproduce sexually to form larvae that settle on the sea floor and develop into anemone-like growths called polyps. If conditions are favorable, a single polyp can bud to form 20 floating jellies. But in hard times, polyps can produce more polyps or retreat into a tough cyst. Then when the environment improves, the waiting polyps can fuel a massive bloom of jellyfish. Bloom triggers seem to be tied to seasonal temperature changes which raises the possibility that warming of the oceans could indeed cause populations to increase.
The bottom line is we do not have enough information on jellyfish population changes to draw any true conclusions. In 2010, biologists created a jellyfish database initiative (JEDI), compiling every scientific jellyfish record they could find and they expect to continue expanding this resource. Citizen scientists are also called to assist through a website called jellywatch.org, through which scientists and citizens can report jellyfish sightings to help fill out the JEDI database.
Maybe telling the students that a jellyfish sighting could be beneficial to scientific research will help calm them down?? HAHA. Not a chance. The screams and flailing those moon jellies elicit are quite extraordinary. Until scientists collect more data, I will patiently wait for the moon jellies to drift away and remind the students to stop screaming, keep their faces in the water, swim around them. And enter the sighting into the database at jellywatch.org
Uye s (2008) Blooms of the giant jellyfish Nemopilema-nomurai: a threat to the fisheries sustainability of the East Asian Marginial Seas. Plankton Benthos Res 3: 125-131.
Condon et al. (2012) Questioning the rise of gelatinous zooplankton in the world’s oceans. BioScience 62 No 2
Graham et al. (2007) Numerical increases and distributional shifts of Chrysaora quinquecirrha (Desor) and Aurelia aurita (Linné) (Cnidaria: Scyphozoa) in the northern Gulf of Mexico. Ecological Studies 193: 239-255
While working with Dr Laurie Richardson of FIU and some of her graduate students, she promised to teach MarineLab instructors how to “suck up” black band disease that is affecting some of our stony corals. While on the search for some black band disease for Dr Richardson to give us a tutorial with, I realized that much of what looks like black band, in fact is not.
The picture above is of a stony boulder coral (Siderastrea siderea) at Grecian Rocks. Dr Richardson was unsure just by looking at the picture but thought what initially seemed to look like black band disease is actually some kind of competition with a sponge. As I have been looking closely for black band disease, I have been seeing this same sponge versus coral interaction on many of our stony corals. But why???
A study published in May of this year looked at sponges on Conch Reef, off of Key Largo (Pawlik et al. 2013). The study noted that as reef building corals have declined, macroalgae covers the greatest surface area on many reefs and sponges have become a primary component of coral reef ecosystems. The authors of the study were looking at bottom-up versus top-down effects of sponges, concluding that the Conch Reef sponge community, which they believe is a good example of most coral reef communities throughout the Caribbean, is structured primarily by top down effects (predation). As overfishing is still a problem throughout the Caribbean reef ecosystem, the loss of spongivores may have a drastic effect on our corals. The authors of the Conch Reef study predict that overfished reefs that lack spongivores will become dominated by faster growing undefended sponge species, which better compete for space with reef building corals. Sponge populations have already been proven to be increasing on Caribbean reefs and as the impacts of climate change and ocean acidification further disrupt marine communities, it seems likely that reef building corals and some macroalgae will suffer greater harm than sponges, which do not form limestone skeletons. At the current rate, Caribbean reefs of the future are likely to become increasingly dominated by sponges.
Nothing with the coral reef ecosystem is simple. Removing a disease is important and can preserve a single coral head but we must get to the source of the issues in order to preserve the entire reef ecosystem – water quality, fisheries management, ocean acidification, etc. in order to have a lasting impact.
Pawlik JR, Loh Tse-Lynn, McMurray SE, Finelli CM (2013) Sponge communities on Caribbean coral reefs are structured by factors that are top-down, not bottom up. PLoS ONE 8(5): e62573.
McMurray SE, Henkel TP, Pawlik JR (2010) Demographics of increasing populations of the giant barrel sponge Xestospongia muta in the Florida Keys. Ecology 91: 560-570.
The next time you see a conch shell, look closely. Students have been noticing octopuses residing in conch shells in the seagrass beds by Grecian Rocks reef. Octopuses are known to feed on conch. Perhaps the healthy conch population at Grecian is attracting more of these cephalopods to take up residence at one of our most visited reefs??
A unique species has been observed by MarineLab instructors during mangrove snorkels recently, the Caribbean box jellyfish Tripedalia cystophora. This interesting cnidarian is not a common sight for us so we were intrigued and needed to learn more about the animal.
First off, how bad is the sting?
Always willing to “take one for the team,” various MarineLab instructors tested out the sting for themselves- responses varied from absolutely nothing at all to a mild itch.
Most interesting fact?
They have 24 eyes! It has been known for well over 100 years that the medusa stage of the cubazoans, box jellyfish, all possess four sensory structures, the rhophalia, each carrying a similar set of six eyes. There has been much speculation on the usage of these eyes in box jellies but T. cystophora are thought to use their eyes for obstacle avoidance and attraction to light, especially useful in exploiting a unique ecological niche, the mangrove roots. T. cystophora are able to avoid mangrove branches from damaging their fragile tissue by utilizing vision, as well as their strong swimming ability. The attraction to light is important because the T. cystophora feed on swarms of the copepod Dioithona oculata which congregate in light shafts created by the mangrove canopy.
Why are we seeing this jelly in Key Largo now and never before?
I have been at MarineLab for over 7 years and have never been lucky enough to see one of these box jellies. It is thought that with the gradual warming of the oceans, a number of marine species from the Caribbean, such as T. cystophora, have been observed moving into areas of the southern and mid-Atlantic coasts of the United Sates. Though this was the first sighting by MarineLab staff, the first specimen of T. cystophora was observed in Florida’s waters in 2009. A single male was discovered in Florida’s Lake Wyman and since then, this jelly has been seen in various areas of southern Florida in greater numbers.
Coates M.M. et al. (2006) The spectral sensitivity of the lens eyes of a box jellyfish, Tripedalia cystophora. The Journal of Ex[perimental Biology 209, 3758-3765
Garm A. et al. (2007) Unique structure and optics of the lesser eyes of the box jellyfish Tripedalia cystophora. Vision Research 48, 1061-1073.
“First report of the box jellyfish Tripekalia cystophora (Cubozoa: Tripedaliidae) in the continental USA, from Lake Wyman, Boca Radon, Florida” by Evan Orellana and Allen Collins.
3 deep sea creatures washed ashore in California within a week: coincidence or an indication of abiotic stresses??
An 18 foot long oarfish was found dead in the waters off of Catalina Island in California on Sunday October 13th, on October 16th a Stejneger’s beaked whale (also known as a saber-toothed whale) washed ashore on Los Angeles’ Venice Beach, and a second oarfish, this one 14 ft long, was found dead on the beach of Oceanside, California on October 18th.
What does this mean?? All sources admit that each of these is an extremely rare find in itself. Oarfish are found in temperate and tropical waters but are thought to dive more than 3,000 feet deep. The beaked whale home range is subarctic waters of the North Pacific from the Bering Sea south to Japan and central California with the center of its distribution around the Aleutian Islands. Needless to say, both the oarfish and the beaked whale are very much under observed and understudied, especially in the shallow waters of Southern California.
A necropsy was performed on the whale- no signs of disease or parasites. Scientists have analyzed tissue samples from the initial oarfish discovered in Catalina and have concluded it died of natural causes.
It certainly could be coincidence, but could these strandings be a sign of something more?
Global climate change? Are the warmer waters affecting these animals and/or their food sources?
Radiation from Japan’s nuclear meltdowns?? Radioactive particles released in the nuclear reactor meltdown in Fukushima, Japan, following the March 2011 earthquake and tsunami were detected in giant kelp in the California coast according to a 2012 published study. Bioaccumulation?
An impending earthquake? According to traditional Japanese lore, oarfish rise to the surface and beach themselves before an impending quake. Mark Benfield, a researcher at Lousiana State University, has noted that shortly before the 2011 Tohoku earthquake and tsunami, about 20 oarfish stranded themselves on Japanese beaches, suggesting the fish could possibly have known that the earthquake was coming. Should Californians be bracing themselves??
Scientists on the West Coast are undoubtedly asking themselves these questions and more as they continue to analyze the specimens. Regardless, having these animals wash ashore relatively fresh and intact is positive in that it gives scientists a chance to learn more about marine creatures that are especially difficult to go out and observe. As for whether these strandings are connected in any way to water quality conditions, only time will tell.
During 2012-2013, MarineLab has assisted John McDermond, a graduate student at Nova Southeastern University, with his Masters project at Rodriguez Key. The purpose of John’s study is to examine population densities of the shallow water hermatypic finger coral Porites divaricata and to determine the mode and timing of its reproduction. Please refer to a former post http://marinelabresearch.wordpress.com/2012/09/21/porites-study-at-rodriguez-key/ for more information on the background and methodology of this study.
While MarineLab has been involved in the fieldwork for this project, John has spend the last year examing his collections back in the lab. The reproductive timing, mode and fecundity of Porites divaricata has been studied using Heidenhains Aniline-Blue for staining. Slides are examined and gametes are photographed and then staged. Divaricata has been confirmed as a brooder, with late stage larvae appearing in March. It appears that peak reproductive timing (based on presence of stage IV oocytes) occurs between December and March. Colonies collected after May have yet to be examined so it is possible that multiple reproductive cycles occur, which is common in brooding species.
A large amount of oocyte resorption has been occurring. No papers to John’s knowledge have quantified the number of eggs undergoing resorption in Porites sp., potentially making this a first time for this genus.
While no statistical tests have been used for population surveys, it does appear that populations are highest at the northeast quadrant of Rodriguez Key. It also appears that populations are highest at the two ends of the key and get smaller as you move towards the center.
MarineLab is proud to be a part of this study and we eagerly await the rest of the results.
For the past few months, MarineLab students have been helping to collect parrotfish feeding data for Dr. Burkepile of Florida International University. He is interested in looking at how much specific species of parrotfish are feeding and excreting to learn more about the use of nutrients on our reefs. Previous research has shown that fish excrement can stimulate coral growth if surrounding coral is healthy and abundant but on algal dominated reefs, the excrement can cause an even higher rate of algal growth. Dr Burkepile and his lab are trying to learn more about the patterns of fish feeding and excreting because he has teamed with the Coral Restoration Foundation and they want to plant the corals in such a way that the fish attracted to the coral can hopefully increase coral growth.