Wednesday, May 28, 2008

Surveying Bermuda's Entire Coral Reef Platform

Since 2004 BREAM has been carrying out the comprehensive assessment of coral reefs across the Bermuda Platform. Multiple transects are surveyed at each site so that the data can be analyzed using standard statistical techniques in order to address ecological hypotheses. Replicate sites have been surveyed across the lagoon, along the shallow rim which defines the edge of the platform, and at many 30-ft deep forereef sites. Over 100 sites have been assessed so far.

At each site a team of 3 to 6 divers assesses both the corals and other animals and plants living on the reef surface, as well as the many kinds of fish swimming over the reef. The data collected to date has been statistically analyzed and the findings are being written into a BZS report that describes the patterns observed in corals, algae and fish as well as implications for management and directions for future research.

Parameters assessed include the following.

  • Species
  • Length on line
  • Width (x & y)
  • Height
  • Surface Area
  • Partial Mortality
  • Disease
  • Bleaching
  • Damselfish bites

Other Benthic Parameters:
  • Coral Recruits
  • Fleshy Algae
  • Calcareous Algae
  • Sponges
  • Soft Coral
  • Invertebrates
Fishes were divided into groups depending on what they ate (called guilds).

The number of species of fish assessed in each guild are as follows:
  • Herbivores (Plant Eaters)
  • Surgeonfish 3
  • Parrotfish 11
  • Damselfish 3
  • and 9 rarer herbivores

  • Invertivores (Snail, Worm and Crustacean Eaters)
  • Grunts 3
  • Snapper 1
  • Filefish 4
  • Butterfly Fish 5
  • Angelfish 3
  • Hogfish 2
  • and 49 others

  • Planktivores 11 (Plankton Eaters)

  • Piscivores (Fish Eaters)
  • Grouper 5
  • Snapper 2
  • Bar Jacks
  • Barracuda
  • And 18 others

Friday, May 23, 2008

Photo Friday

White grunts schooling over a fire coral.

Thursday, May 22, 2008

Bob Ballard makes the case for exploring the oceans

Quote: NASA explores space; NOAA explores the oceans

NASA budget for 1 year = NOAA budget for 1600 YEARS!!!


Watch the video - more on this topic with a Bermuda angle in next post

Tuesday, May 20, 2008

Assessing functional groups of hard corals across Bermuda

Project context
Coral reefs are degrading across the Caribbean, and yet all species of corals do not seem to be equally affected. Examination of the functional traits that promote the persistence of some species despite the demise of others is needed if we are to understand why reefs are in decline. Corals in Bermuda were classified into functional groups, according to the manner in which they exhibit the primary functional characterisitics of growth, reproduction and defense. Assessment across reefs located over the North Lagoon determined that species within each functional group of coral responded to environmental gradients in a similar, theoretically-predictable manner.

To determine how functional characteristics of each coral species affects the assemblage structure of corals on reefs located across environmental gradients of stress and disturbance. Specific objectives include:
  • Determining critical traits to use for classifying corals into functional groups
  • Assessing coral assemblage structure over gradients of varying light, sedimentation and wave energy.
  • Statistically assessing significant patterns and comparing results to those predicted by theoretical models.

Recent findings
Analysis of coral abundance data from 64 sites on 18 reefs located across the North Lagoon reveals that different traits confer adaptive advantage in different environments. Key findings include:

  • Coral assemblage structure and diversity varies greatly over small spatial scales due to quantifiable changes in light level and current speed
  • Distributions of key coral species are determined by the way they each are adapted to different environmental conditions and also they way the minimize competition within locations
  • Trade-offs between growth rate, aggression and reproductive rate allow species to coexist locally and regionally
Patterns of distribution that appear random are actually deterministic when viewed at the correct spatial scales and with the right statistical filters. Some level of redundancy in ecological function between species within functional groups allows corals to provide ecosystem services at an assemblage level despite changes in assemblage composition from patch to patch.

Reference: Murdoch TJT (2007) A functional group approach to predict the assemblage structure of hard corals in Florida and Bermuda. PhD Dissertation. University of South Alabama 300 pp.

Friday, May 16, 2008

Photo Friday

A finger coral in a seagrass bed.
This is a new species record for Bermuda,
and so far we have only found it in one bay!

[click image to enlarge] (c) 2005 T. Murdoch

Thursday, May 15, 2008

Why do we use a Geographic Information System?

In a recent post we described how we manually converted a high-resolution aerial image mosaic of the Bermuda reef platform into a set of georeferenced polygons - creating a digital map of all the reefs around the island.

There are many benefits to having an electronic map instead of a paper map.

When each patch reef was added to the database, they were each assigned a number. This means every single patch reef in Bermuda now has a unique ID tag that can be used to name them.

In this section of the aerial image, abouto 1km wide,
you can see the ID number of each patch reef.

Having an ID number for every reef helps scientists and resource managers, as it gives another way to distinguish each reef.

Proximity Mapping
We can ask the GIS programme to select reefs within a certain distance of another mapped object. For instance, if we have a layer representing the Island, we can ask the programme to select and highlight all of the reefs that are within 1 nautical mile from shore. This then gives us a map of all of the reefs where spear fishing is not allowed. We can also then ask the computer to give us a data table of the ID numbers of each reef within this protected zone.

A map of all the patch reef in the No Spearing Zone.

Size, Shape, Isolation, etc etc...
We can also get the programme to highlight patch reefs based on a wide range of other parameters, many of which it calculates from the polygons around each reef. This means we can get data from the map that we did not have before we made it.

For instance, we can get the programme to select reefs of a specific size, or only reefs that are round, or reefs that are near other reefs. We can then use this information to guide research: Reefs of different sizes may contain different numbers of fish species. Round reefs have a smaller edge exposed to the surrounding water compared to an elongated reef, and therefore might have alternate rates of larval fish and coral recruitment. Reefs near other reefs also may differ in fish and coral assemblages relative to reefs that are isolated.

A map of patch reefs in White Flats colour-coded by size (area). Click image to enlarge

So - why do we use the GIS maps instead of paper?

Because paper maps are static, but GIS maps are DYNAMIC!!!

Monday, May 12, 2008

Monitoring the Water Quality of Bermuda’s Coral Reefs and Seagrass Beds with NASA Satellites and UW Sensors:

Project context
When sand and mud get stirred up in the ocean by either ships or storms, it has a negative affect on the plants and animals that live there. The sand smother and grind into the surface of the plants and animals. Also when up in the water in thick clouds suspended sand blocks the light reaching the sea floor that the plants and animals need to grow or to see.

In order to know how the organisms living in the water and on the sea floor are being affected by the amount of sand and other material is suspended in the water, scientists usually go out in boats and measure water clarity and the amount of suspended sediments in sea water. These measures through time are similar to underwater weather reports and tell scientists how healthy the ocean is through time and from place to place.

However, new methods and instruments such as remote sensing using satellites, and aerial photography from air planes, have expanded the capacity for studying biological processes, as well as the effects of geophysical and chemical factors such as temperature and nutrient concentrations on natural environments.

Gerardo (front) checks the data uploading into
the laptop computer from an water particle sensor (see below)
that Dave (back) has suspended below the boat.

Gerardo Toro-Farmer, a graduate student at the Univesity of South California at Los Angeles is working with BREAM as well as collegues at USC-LA and NASA to develop different in-situ (in place) and remote-sensed (by satellite) light measurements. He hopes to develop a reliable, low cost, and low effort way to be able to measure water clarity and suspended particulate load across Bermuda’s harbours and out across the coral reef lagoon to the deep sea around us.

An underwater sensor which uses lasers to
count and measure the size of particles in the sea.

Optical measurements will be compared between in-place instruments and data collected by satellites, to study the effects of sediment resuspension events on the water column optical properties on coral reefs and seagrass beds. In this research Gerardo will address two questions:

Question 1: Can in-situ optical measurements be utilized to estimate resuspension and movement of bottom sediments from navigation channels?
Question 2: Can remotely sensed data be used to identify and quantify resuspended sediment plumes that are produced by ships traveling across the Bermuda reef lagoon in shipping channels

Anticipated Results
Gerardo expects to find a simple relationship between suspended sediment load and remotely-sensed reflectance in the red and infrared channels of NASA satellite imagery.

Stereoscopic imagery from satellites should clearly reveal vessels and their wake. This information combined with satellite mapping of suspended sediments will likely provide valuable information on the contribution of ship traffic to resuspension and associated redistribution of sediments in the lagoon.

False color images created with loggers light intensity measurements will probably show a gradient from lower light level values closer to the channels during periods of high ships traffic, to higher values (higher light intensity) far from the channels and during low traffic periods. This gradient will be also observed with satellite images.

NASA's AQUA satellite, which is used to assess water quality in Bermuda
and around the globe from outer space.

Friday, May 9, 2008

"Damn it Jim, I am a Doctor, not a SCUBA Diver"

Unlike Bones, who used to say silly things like this on the original Star Trek series way back in the dark ages, we on the BREAM team ARE SCUBA Divers (and some are doctors too) - AND we get to hang out with surgeons too (well, ok - surgeon fish). Like medical doctors we are also worried about diseases, temperatures and whether our patients are pale or icky-looking.

This BREAM scientist is counting fishes and recording her results on the yellow clip board.

The ecological health of a coral reef depends upon the condition of all the corals, fish, algae, sea urchins, gorgonians, sponges and other critters that live on it. When a reef is healthy the amount of algae is low, corals are abundant, and there are numerous predatory fish, as well as fish that eat algae (plants) and fish that eat water-borne plankton.

A healthy reef off South Shore.

When we survey a reef, we take measurements just like a doctor does. We count and measure the size of corals, sponges, sea urchins and fishes to see if they are growing big and strong. We check each coral for diseases which can harm the coral, and look to see if each coral head looks pale due to overheating or overexposure to the sun.

A sick coral with "yellow-band" disease along its right side.

By mapping these factors across large areas from year to year we are able to provide an "annual check-up" on the ecological health of our coral reefs - which then guides the management and research activities of government agencies and local scientists.

Lots of fish, corals and gorgonians make for a healthy reef!

Thursday, May 8, 2008

Pretty Picture Thursday

A juvenile Blue Tang poses near a Brain Coral
[click photo to enlarge]

Wednesday, May 7, 2008

Seaweed blenny

A well camouflaged seaweed blenny in a sponge.

Tuesday, May 6, 2008


One may wonder why we would choose to name ourselves after the Bermuda Bream, considering some of the other, less pleasant names we Bermudians call the fish.

Well, there was the pragmatic reason that "Bream" started with a B - so we could start our name with "Bermuda"...

However, another draw was that the Bermuda Bream is actually an endemic fish, meaning it is a species found in Bermuda and no where else. Yep - our bream are ours alone, at least according to Caldwell (1965), who first stated this assertion. It' species name is Diplodus bermudensis.

That said, there are sister species found across the Atlantic, including one in the Mediterranean called the White Bream (Diplodus sargus sargus) which looks remarkably like our guy. I took a photo of the specimen below in the Monaco Aquarium a few weeks ago.

There are also bream over in the US and Caribbean, and down to South America, but with the much nicer name of Silver Porgy.

Not surprisingly there is some controversy about whether our local species is an endemic or not. In the book "Fishes of Bermuda", Smith-Vaniz et al. mention that there is still a need to fully compare the Bermuda fish with the similar fish from the rest of the Western Atlantic.

Despite the local reputation that bream are a bottom-feeding fish and therefore of low food quality, in many parts of the world similar species are actually targeted, although truthfully this may be because there are no better fish left to eat. There have even been attempts at rearing other bream using aquaculture techniques. Certainly some people are eating bream in Bermuda. Also, the recent study on mercury in Bermuda fish found that mercury levels are low in fish lower on the trophic ladder, which bream are, so perhaps those eating bream locally are on to something!

Perhaps we could re-market the poor bream by calling it a Bermuda Porgy, although then again that would mean we here at BREAM would lose our spiffy mascot.

Reference: Caldwell DK (1965) A new sparid fish of the genus Diplodus from Bermuda. Fieldiana Zoology 44:217-225.

Monday, May 5, 2008

Mapping Bermuda's Coral Reefs

BREAM, as part of the Bermuda Biodiversity Project at BZS, has developed the most comprehensive maps of Bermuda's coral reefs and other marine habitats that exist. In this post we will describe how we mapped all of the 35,000 patch reefs in the North Lagoon of Bermuda.

Our goal was to create a Geographic Information System (GIS) of all the reefs found around Bermuda. A GIS is a computerized map that also contains information about each object mapped. Computerized maps are better than paper maps because once you put all the information you know into the program, you can then ask it to tell you new information which the program can calculate based on what you told it. Some questions you can ask a computerized mapping programme are listed at the bottom of this post.

Before we mapped the location of each reef into a GIS (also called a geo-referenced map database), we needed a set of images of the entire Bermuda reef platform. The BBP, with assistance from the Dept. of Conservation Services, commissioned an air plane to fly over the reef platform in a regular pattern , while taking geo-referenced photographs at regular intervals. Once the air plane landed the set of photographs was taken to a computer laboratory where the images were scanned in, and put together to form a mosaic. We sell a poster or mouse pad of this image mosaic of the island and surrounding coral reefs at the BAMZ Gift Shop.

Mosaic image map of the island of Bermuda
and it's surrounding marine habitats. (c)1997 BZS.
Click Map to Zoom

Since the mosaic image was in a computer the exact location where each picture was taken on the Earth could be determined. This meant that we could then use the same images in a mapping computer programme and create a line map of each reef in a way that kept track of where each reef was located. As you can see in the image below, by zooming in on the aerial image until we can see each small reef (1), we can then draw a line around each reef (2), and in this manner create an image of the reefs that is a picture, not a photograph (3)

The three steps we take to map each reef from the aerial image.

We followed the same process across the entire image mosaic, until all reefs were mapped into the computer program. Now all the reefs are mapped we can make charts of the reefs, such as the one below.

A chart showing the location of all 35,000 patch reefs
in the Bermuda lagoon. (c)2007 BZS
Click Map to Zoom

We can also use the same computer program to tell us things about the mapped reefs. For instance, we can ask the mapping program to tell us the following:
  • Count all the reefs
  • Show the location of all the reefs of a certain size
  • Show all the reefs that are within 1 nautical mile from shore
  • Tell us the location of any reef in Bermuda
After mapping all the reefs in the computer, we then went out to lots of reefs and surveyed them to determine how many corals, fishes, sea urchins and other animals were on each reef. By going to lots of places we can then use the same mapping programme to produce maps showing how each organism is distributed across the whole reef platform. We will describe our maps of corals and fish in another post, coming soon...

Friday, May 2, 2008

Wonderous Whip Morays

Studying Bermuda's Own Spotted Eagle Rays

A BZS-supported graduate research project undertaken in 2006, 2007 and again this summer by Matt Ajemian, a student at the U. South Alabama, Marine Science Dept, and the Dauphin Island Sea Lab's Fisheries Lab

Project Context
The spotted eagle ray (Aetobatus narinari), locally known at the “Whip Moray”, is fairly abundant over seagrass beds and sand flats of Bermuda. The Government of Bermuda has expressed interest in placing spotted eagle rays on the Protected Species List – however insufficient information of their population status and ecology has prevented any such action. The urgency for A. narinari data has become critical as they are potential predators of conch and scallops, both of which are also undergoing restoration from overharvest in Bermuda. Rapid population increases of other rays in North America (Science journal pdf) demonstrate that rays can impact shellfisheries quickly - highlighting the need for understanding the ecology of spotted eagle rays in Bermuda as soon as possible.

Matt (right) and "Flookie" (right) prepare an Eagle Ray for tagging with a tracking device

In conjunction with Dr. Thad Murdoch (BZS) and Chris Flook and his team (BAMZ), PhD student Matt Ajemian (DISL, University of South Alabama) is trying to understand the ecological role of Bermudian spotted eagle rays. Matt is from Long Island, New York, and has been interested science, and in particular the biology of sharks and rays since a very young age. He studied the feeding behaviour of deepwater chain catsharks as part of his Masters degree at Hofstra University and studies the foraging ecology of cownose rays in the northern Gulf of Mexico.

Specific objectives include:

  • Determining populations size across Bermuda
  • Assessing their diets, foraging behaviour and motion across Bermuda using ultrasonic tracking transmitters and datalogging hydrophones.
  • Measuring the ecological role and impact of eagle rays on shellfish stocks

Recent Findings
Since May of 2007, the research team has captured, photographed and measured 13 spotted eagle rays, all of which were released harmlessly back into their native environment. Key findings include:

  • Acquisition of basic biological information on these animals (size, sex, maturity state, food habits)
  • Tracked the movements of eagle rays throughout Harrington Sound and Flatts for 2 months, to show possible aggregation areas and residency within HS

Spotted eagle rays are probably slow-growing, late-maturing species that produce few pups per litter. These reproductive parameters make spotted eagle rays vulnerable to exploitation. Our continued work on this charismatic and potentially ecologically important species will provide critical data for conservation purposes while bringing information on living resources to Bermuda’s public eye.

Thursday, May 1, 2008

What is Good for Grunts is Good for We Bies too!

Great News! Yesterday, Elvin James, Minister of the Environment and Sport, announced the designation of a temporary No Fishing Area north of Fort St. Catherine for the 2nd year in a row. This protected area was created in order to protect a Blue-Striped Grunt spawning aggregation (SPAG) that has been heavily fished during previous years.

Blue-striped grunts play an important role in our marine environment, as they are predators of small crustaceans and other invertebrates. Grunts often spend the day in schools on coral reefs, and then go out to neighbouring sandy areas and seagrass beds to feed at night. Studies have shown that when the grunts return to their reef home in the day time they bring important nutrients back with them that aid in coral growth. In doing so grunts act as a means for nutrients to move between the two habitats and thus act to enhance the ecological resilence of coral reef ecosystems overall.

Fishing a spawning aggregation is the very definition of an unsustainable practice. Killing fish just before they reproduce prevents the production of new fish to replace the adults. Most countries now ban fishing at known spawning aggregations. Historically in Bermuda overfishing of Nassau Grouper at spawning aggregations resulted in the ecological extinction of the fish in Bermuda (reference), which might be why fishermen would even want to catch grunts these days.

Hopefully by protecting the spawning aggregation of the grunts, these fish will survive on our reefs for years to come.