Ecological Assessment of Marine Invertebrates
The need for conservation of coral ecosystems throughout the world requires knowledge concerning the ecological requirements of species that make up the system, causes for the loss of any of the component organisms, and the requirements for the survival of remaining species. The collection of systematic information concerning what taxa are present, or biodiversity assessment, is a prerequisite for determining the factors previously mentioned. The task of conservation is further supported by an ongoing monitoring program, which uses the biodiversity assessment as its baseline for detecting changes through time.
Historically, the biodiversity assessments and monitoring programs for coral reefs have focused strictly on the charismatic fauna such as cnidarians and fish. Coral reefs are compared to rainforest habitat when referring to their biodiversity. Rainforest ecosystems are viewed from the perspective of the canopy components but are made up of a wealth of less charismatic fauna that contribute greatly to the biodiversity. In the case of coral reefs this is also true; the cryptic sponge, mollusk, echinoderm, crustacea, annelid, bryozoan, and tunicate fauna are an integral component to the overall biodiversity.
The Coral Reef Ecosystem Investigation (CRED) program of the National Oceanic and Atmospheric Administration-National Marine Fisheries Service, Honolulu Laboratory includes a marine invertebrate component as part of its rapid ecological assessment (REA) activities in the tropical Pacific. The marine invertebrate component is done in conjunction with surveys of fish, corals, and macroalgae to create a complete benthic survey of coral reef areas that are included in the scope of the program.
- The goal of the marine invertebrate component of the rapid ecological assessment is to collect both quantitative and qualitative information concerning marine invertebrate organisms other than corals.
- Surveys are centered around transect locations chosen to cover the greatest variety of habitats and are conducted in conjunction with efforts focusing on assessing macroalgae and coral communities.
- At this time, the product of this effort is a species inventory that will provide baseline information to support future monitoring activities.
- Also, specimens will be collected that will be vouchered in museum collections that can be accessed by researchers around the world.
Importance of Systematic Inventories on Coral Reefs
The marine invertebrate fauna of coral reefs represents a group of animals that are numerically dominant in their habitat and in some cases represent taxonomic groups that are only represented in the marine environment. It is the assumption of many nonscientists that marine biologists have adequately described all species in all the habitats of the world’s oceans. New species of marine organisms are being described all the time in extreme habitats such as hydrothermal vents but also in more extensively studied habitats such as coral reefs. In addition to these new species descriptions, the expansion of knowledge concerning the ranges of known species is also an important task that is integral for the spectrum of conservation ranging from single species up to the level of ecosystems.
Marine invertebrate collections housed in natural history collections throughout the world are the main source for the information mentioned in the previous paragraph. These collections housed in museums and universities throughout the world are extensive but still there is ample room for augmentation and addition to these resources. The present knowledge concerning systematics of marine invertebrates comes from the study of preserved specimens in these institutions, which were provided by various historical expeditions and individual efforts that focused on the collection of biological specimens in a variety of habitats. No single institution has collections that achieve complete coverage of all taxonomic groups and habitats. This is why marine surveys are as important today with our extensive knowledge as they were a hundred years ago.
In addition to providing resources for taxonomic pursuits, marine invertebrate surveys document species that have use as bioindicators. Variations in populations of some species groups can indicate subtle changes in environments based on the different physiological characteristics of the diverse assemblage of marine invertebrates in reef habitats. For example, the abundance of some marine invertebrate groups such as tunicates can indicate poor water quality, and many filter feeders can be used to track contaminants due to their concentration of trace metals. A baseline species list with accompanying abundance data is the first step towboard using marine invertebrates as indicators of change in an environment. This baseline information combined with a continuous monitoring program at set intervals can detect physical and chemical changes such as pollution and sedimentation and biological changes such as alien species introductions.
The activities of marine habitat surveys such as the Coral Reef Ecosystem Investigation provide benefits and information that are not immediately apparent due to the complexity of large amounts of information collected in a short period. The collection of hard data in the form of species counts, distribution, abundance, and oceanographic parameters provides baseline information that is useful in supporting decision-making processes. Specimen collections archived in museums and universities provide information useful for determining actual biodiversity values for coral reef habitats.
Marine Invertebrate Sampling Methods
1. Standard Rapid Ecological Assessment (REA)
The marine invertebrate zoologist participant of the benthic REA team enters the water along with coral and algal biologists and conducts quantitative counts of macroinvertebrates 1m to either side of the first two (of three) 25-m transect lines. For any species that cannot be identified in the field, a representative specimen is collected for later identification.
After the completion of the two transects, a roving swim is conducted in the general area to collect qualitative data for rare and cryptic organisms and to survey any additional habitats present at the site; e.g. ,sand, sea grass, pavement, etc. This is accomplished by swimming a zig-zag pattern that extends roughly 5 m on either side of the two transect lines.
Also at this point, a variety of specialized collections will be taken:
- Additional collections of organisms unable to be identified in situ
- Sand/Sediment samples for infaunal organisms
- Rubble, dead coral, and algal collections for symbiotic organisms or substrate-specific inhabitants
2. Intertidal sampling
Surveying in this habitat will greatly depend on the current, wave conditions and field scheduling; therefore this will not be possible at every location. In the case of a suitable sampling environment there will be two 25-m transect lines laid at both a littoral zone and a subtidal zone, all parallel to shore.
The two littoral zone transects will be laid at 0.5 m depth and a combined qualitative and quantitative count will be done 1 m to each side. The two subtidal zone transects will be laid at 1m depth and surveyed in the same fashion. Also, depending on site topography and if time allows, two 25-m transects will be laid perpendicular from the water's edge and surveyed with the same procedure.
For all invertebrates on the transect lines that could not be identified, a representative specimen will be collected. Upon completion of a transect at each depth, there will be a general search of the area for additional organisms not seen on the transects and the specialized collections listed above will be carried out.
3. Treatment of Samples in the Field
Where possible, and time permitting, all collected organisms will be sorted by higher taxonomic level (e.g., molluscs, crabs, shrimp, tunicates, etc.) in the field lab. Individual specimens that need further analysis will be preserved with methods appropriate for the specific taxonomic group.
Additional specimens will be obtained from the various substrata collected for the purpose of identifying cryptic organisms. These samples are processed in the following ways:
- Rubble is placed in a dilute formalin bath to dislodge small invertebrates. Large pieces of rubble are broken apart using a hammer and chisel and all pieces thoroughly rinsed with fresh water before storage in 75% ethanol.
- Algae will be washed in either dilute formalin bath or under running freshwater. All invertebrates will be collected on 0.5. mm sieve and preserved in 75% ethanol.
- Sand samples will be placed in trays and air-dried. Micro-molluscs will be sorted from sand by hand using forceps and a dissecting microscope. A 10 cc subsample of sand will be sorted for each site.
Species that cannot be identified in the field will be brought back to the research vessel for further analysis. Organisms that can be identified during this time will be returned to the field the next day and species that cannot be identified will be saved for later analysis at Bishop Museum in Honolulu, Hawaii. Specimens saved for identification will be preserved in ways suitable for each taxonomic group.
The analysis at Bishop Museum will involve the use of taxonomic literature for tentative identifications and then specimens will be sent to experts throughout the world for confirmation of these identifications. Both the Bishop Museum registrar and Invertebrate Zoology collections manager monitor this loan process until the specimens are returned.
This post-processing activity and data management require the focus of an invertebrate zoologist involved in the field collections and a part time technician for a period of roughly one year. The specimens will be permanently housed within the Bishop Museum Invertebrate Zoology collection at the end of the process.