Methods: As mentioned at the beginning, our survey lasted only two weeks (compared to professional assessment programs may take up to eight weeks), thus, this report is by far not complete at all.
The expedition took place aboard the MV Marlin-1, a 18m motor boat owned and operated by Lee and Wayne Thompson (NZ). The vessel was equipped with a long range cruising capacity, ample scuba tanks, an efficient air compressor, and a small 4m long dingy with an 18kW external engine.

 


Diveboat Marlin I (50kB)
Useful equipment:
     i) Plastic ruler marked in cm/mm
     i) Laminated plastic slate and pencil for under water notes
     i) Underwater camera with strobe
     i) Underwater hand lens

It was essential to trim down the overflow of the overwhelming visual input in order to obtain useful information and to make this short report comprehensible enough. Furthermore, the incredible diversity present in the waters of PNG, made it impossible for a two week-field course to cover each phylum extensively; soon after the first orientation dives at Black & Silver and Little China reefs, it was more than obvious that each group had to narrow down their individual programs; our reflections regarding biodiversity ultimately were restricted to the order of scleractinia (the stony corals), and to the likewise complex phylum of porifera (less extensively surveyed than corals).

 

 


Useful tools: U/W-camera, plastic slate with soft pencil, a hand held lens, and plastic slide calipers (80kB)

In-situ Identification: The Reef is never familiar. It is too complex to grasp it, likewise is its size not easily imagined. For some biologists the Indo-Pacific is like a giant multi-layered jigsaw puzzle containing numerous distribution patterns of the different species - many of them extending all the way from the Red Sea to the eastern Pacific.
In addition, it should also be remembered that both corals and porifera are colonial organisms (with few exceptions) that show much variation from one place or habitat type to another.
It is the aim of this paper to encourage in-situ identification wherever possible. Even with aids like SCUBA and underwater photography there are several problems as corals are still classified principally on skeletal features, whereas sponges almost exclusively by their spicules.
Often, taxonomic clues are obscured by living tissues, while others are so small as to be difficult to distinguish under water. This difficulty can be partly overcome by carrying a magnifying lens or by removing a small portion of the colony - possibly dead or fragmented pieces only - for examination above water. This should be done with great care in order to minimize damage, and never in protected areas where collecting restrictions apply.
Many genera are distinct and can be readily recognized from good photographs. Accordingly, laminated colored prints were taken under water as an extra aid for identification; while others, less conspicious require both a photographic match along with detailed notes. It takes several minutes to complete this exercise, and since time under water is limited then it is essential to be suitably prepared before entering the water.

The "Aid" of Color: All organisms have three colors - what you see under water, what you see when you collect them and what comes out in a photograph. The best way one can overcome this problem is that the diver has has to collect a piece of blue-colored organism at about 10m depth, then to watch it while swimming upwards toward the water surface. It will gradually change color and be mauve or pink before reaching the surface. This is because sea water acts as a selective light filter, first removing the longer wave lengths (reds), then in succession the other colors across the spectrum until, in deep water, everything is a dim bluish-gray. The camera flashlight is designed to correct this effect and the resulting photograph is usually a mixture of natural and artificial (flashlight) color. Often the photographed color is unpredictable and the bright-color patterns of some organisms underwater stubbornly resist the efforts of the photographer to record them. A certain proportion of marine fauna have very specific colors or color patterns and these may help in identification. In the case of corals and sponges, the majority of them have very variable colors (especially in different geographical areas), and thus are seldom useful in taxonomy.

Methodology for Scleractinians (corals): More than 65 species have been found in Caribbean reefs of the Atlantic (there are both shallow, fast-growing forms and deep, massive, slow-growing forms, living at a maximum depth of about 30m). The Great Barrier Reef (GBR) of the Indo-Pacific has 350 named coral species. Milne Bay Province harbors an extensive area of coral reefs that houses roughly 360 species within 68 genera, itself part of 15 families (Veron 1998). Colony development has allowed corals to be free of many of the limitations of the solitary individual. It allows them to build complex structures which are variable in shape, size, and design. Corals on the upper slope, exposed to continual pounding from the ocean waves, are small, stunted and solidly constructed. Further down the slope, where wave action is less, coral colonies become larger and more delicate. Still deeper, where there is no wave action but light availability becomes reduced, the shapes of colonies are different again and broad delicate tables and plates and lightly structured branching forms become the most common. Growth-form variations resulting of genetic and abiotic influences must be taken into account when identifying a coral. Therefore, the species is the sum of all these varations. As a result, it is not surprising, that corals earned themselves a bad reputation amongst biologists. Although, at species level, the corallite structure is of essential importance, it might be essential to work along with several samples at once to differentiate between true species and simple growth form variations. The relatively few collected specimens consisted almost entirely of already broken hard coral fragments, that have been bleached, visually analyzed in order to verify the corallite structure, and eventually determined them down to a Genus level.

Coral specimens require to be bleached; the characteristics of the skeleton are then used to identify it; such specimens can almost always be readily identified to genus level. Species are recognized easily in some genera, while in others, especially the big genera Acropora, Montipora, Porites and Fungia, identification may be difficult. In all cases where there are difficulties, the reader should use photographs, descriptions, and taxonomical keys in combination with each other. The keys guide the reader to the correct species or group of species are designed to be used with the species descriptions.

Determination of corals requires the colection of the following data:
     i) General features: solitary / colonial; attached / unattached; size, color, growth-form;
     i) Corallites: arrangement, shape, size, and pattern of asexual reproduction;
     i) Septa and costae: arrangement; exsert / insert; margins;
     i) Pentheca / coenosteum: general features;

 


Global coral diversity (according to Veron, 1997 - 80kB)

Methodology of Porifera (sponges): In the field, a few sponges can be easily identified to genus level by features that can be seen with the unaided eye, however, other genera require a microscopic investigation of spicules and other structures in order to establish their identity. In addition it has to be kept in mind that morphological features may differ substantially according to the regions. Relying on underwater photographs may be useful to document growth forms, but they imply great potential for errors in species identification. In order to examine the finer features, it is necessary to collect specimens or a sample of them. Most colonies can regenerate if only a part is collected; however, with small colonies, the whole specimen may have to be collected. Any collected specimen is best stored by placing them into 70% ethanol in fresh water, which not only does the fixation procedure (preventing bacterial action besides stabilizing proteins) but also preserves the sample (maintainig its tissues in a fixed state) for a very long time. As most specimens contain CaCO3 or SiO2 spicules, it is not advisable to use formalin (usually 40% formaldehyde) as it gradually oxidizes to formic acid over longer periods of time. The carbonate structures of such samples stored in formalin become chalky white and crumble easily besides loosing the finer surface structures (this is likewise valid for the long term storage of coral samples).
According to a sponge's taxonomic rank, sponges have differently shaped spicules that also differ in its composition. Thus, species determination can easily be done by immersing a thin slice of the sample for about 24 hours in concentrated Danchlor solution; this will dissolve the organic matrix and expose the spicules that can be analyzed under a microscope. Merging the microscopic spicule design with macroscopic external features provides good evidence for species assignment. In this way, several sponges can be easily distinguished such as Cinachrya, Coelocarteria, Xestospongia, and Oceanapia.

 

PART-II Porifera (L. pore bearers):

Sponges are a diverse group of animals, with about 5000 species known across the world. They are primarily marine, but around 150 species live in fresh water. Sponges have cellular-level organization, meaning that their cells are specialized so that different cells perform different functions; similar cells are not organized into tissues and bodies but are a sort of loose aggregation of different kinds of cells; thus, the simplest kind of cellular organization found among parazoans. Sponges live by pumping large volumes of water through their bodies and filtering out minute organisms and organic particles as food. The inhalent canals originate as small pores (ostia) on the outer surface of the sponge and lead to spherical chambers. These chambers are lined with choanocytes, cells with whip-like flagella that beat in rhythmic waves to pump water through the body in one direction. Water carried into the sponges is filtered for food particles and oxygen and is then expelled through one or several exhalent pores (oscules). Sponges are either radially symmetrical or asymmetrical. They are supported by a skeleton made up of a protein collagen and spicules, which may be calcareous or siliceous, depending on the group of sponges examined. Skeletal elements, choanocytes, and other cells are imbedded in a gelatinous matrix called mesoglea (Gk. mesos, middle; glia, gleu = mesohyl). Sponges capture food (detritus particles, plankton, bacteria) that is brought close by water currents created by the choanocytes. Food items are taken into individual cells by phagocytosis, and digestion occurs within individual cells.

Reproduction is both sexual and asexual and is mediated by a variety of methods, including budding, fragmentation and a resting stage known as the "gemmule". In many cases, sponges can be cut into pieces and each will reorganize itself to survive as a separate individual (this phenomenon forms the basis of the culture of the commercially valuable "bath sponges").
Many individuals are hermaphrodites, producing both eggs and sperm. In sexual reproduction, sperm are released into the water; eggs may be released (oviparous) to undergo fertilization and development in the water or are retained and fertilized inside (viviparous) the sponge. In some species there is synchronous release of sperm and eggs, that develop into larvae after fertilization (zygote). The larvae swim or creep along the bottom for periods of up to several days, aiding in the dispersal of the offspring.

 


Sponge Anatomy (160kB)

Asexual reproduction is by means of external buds. Some species also form internal buds, called "gemmules", which can survive extremely unfavourable conditions that cause the rest of the sponge to die. Gamet maturation takes place in the mesoglea. Male gametes are released into the water by one sponge and taken into the pore systems of its neighbours in the same way as food items. Spermatozoa are "captured" by collar cells, which then lose their collars and transform into specialized, amoeba-like cells that carry the spermatozoa to the eggs. Some sponges are monoecious (individuals produce both male and female gametes); others are dioecious (sexes are separate). In most sponges for which developmental patterns are known, the fertilized egg develops into a blastula, which is released into the water (in some species, release takes place right after fertilization; in others, it is delayed and some development takes place within the parent). The larvae may settle directly and transform into adult sponges, or they may be planktonic for a time. Adult sponges are always sessile.

Morphologically, sponges fall into three main groups according to how their bodies are organized. The simplest sponges are the asconoid sponges. These are shaped like a simple tube perforated by pores. The open internal part of the tube is called the spongocoel; it contains the collar cells. There is a single opening to the outside, the osculum into which all pores converge once the water has been filtered through the collar cells. The osculum is thus the main outstreaming opening of a sponge. The next more complicated group is that of the syconoids. These sponges tend to be larger than asconoids. They also have a tubular body with a single osculum, but their body wall is thicker and the pores that penetrate it are longer, forming a system of simple canals. These canals are lined by collar cells, the flagellae of which move water from the outside, into the spongocoel and out through the osculum. The third category of body organization is leuconoid. These are the largest and most complex sponges. These sponges are made up of masses of tissue penetrated by numerous canals. Canals lead to numerous small chambers lined with flagellated cells. Water moves through the canals, into these chambers, and out via a central canal and osculum.

 


Body morphology - asconoid, syconoid, leuconoid sponges (110kB)

Sponges are commonly referred to as "simple" or "primitive", but they are in fact, very successful and highly evolved organisms which have managed to adapt and survive longer than any other multicellular animal. Sponges lack muscles, nerves and body organs, but are sedentary filter-feeders. Skeletal support in sponges is provided by a network of hard spicules, flexible fibers, foreign sand or a combination of them. Spicules are small crystalline structures made of either calcium carbonate (in the mineral forms calcite or aragonite) or silicon dioxide (glass). In addition, collagen and spongin (protein) fibers produce the soft, classically "spongy" skeleton typical of many sponges.

Class Calcarea (L. calcarea, limestone) group sponges that have calcium carbonate spicules in the mineral form as calcite rather than siliceous skeletons. Their spicules are made up of calcium carbonate; they are simple in structure or may have up to four rays. Calcareous sponges are small and delicate with a crunchy texture, due to a lack of spongin and collagen, they occur in limited numbers in all marine environments. Members of the class Calcarea are small. Most are tubular or vase-shaped, and they can have asconoid, syconoid, or leuconoid organizations. All species are marine.

 


Leucilla nuttingi (40kB)

Class Demospongiae (Gk. demos, bond; spongos, sponge): this group include both fresh water and marine species and is by far the largest and the most diverse group of sponges. Demosponges one or both of these skeletal components may be absent. Their spicules are siliceous but not six-rayed; the spicules in some forms are partly or completely replaced by skeletal elements made of spongin (a sponge protein). The canal systems are leuconoid. Demospongiae includes the familiar tube, vase, barrel, and fan sponges, as well as a large number of other species.


Xestopsongia sp. (120kB)

Class Hexactinellida (Gk. hexa, six; aktinos, ray) are commonly called glass sponges, as they have distinct siliceous spicules with six rays and are united with each other as to form a network. The body is usually cylindrical or funnel-shaped. Most Hexactinellida are syconoid or leuconoid in body organization. All species are marine and are seldomly found at depths less than 50m.


Sceletal features of Venus flower Euplectella sp. (45kB)

Class Sclerospongiae (Gk. scleros, hard; spongos, sponge) these sponges are sometimes included in the class Demospongiae. They have a massive calcareous basal skeleton, with the living tissue mostly within the skeleton (extending outward very slightly). These sponges have siliceous spicules and spongin fibers like those of the Demospongiae. Their body plan is leuconoid. Sclerosponges are found in marine environments, usually in association with coral reefs. Notorious for their biodegradive capabilities are sponges of the genera Cliona, Anthosigmella, and Spheciospongia, in the order Hadromerida, and Siphonodictyon (Haplosclerida). These sponges actively bore into the calcareous substrate of both limestone substrata and precipitated CaCO3 of scleractinian corals.

 


Siphonodictyon coralliphagum bioeroding a Diplora sp. of the Caribbean (115kB)

Sponges are found in virtually all aquatic habitats, although they are most common and diverse in the marine environment. They must compete with other bottom dwelling invertebrates for attachment sites and living space on hard surfaces. They often succeed through "chemical warfare", probably also to discourage predators. Certain other marine animals take advantage of this characteristic of sponges by placing adult sponges on their bodies, where the sponges attach and grow. The chemicals also probably play a role in inter- and intra-specific competition among sponges and other organisms. These are released into the near environment to ensure themselves space in the marine ecosystem. Some of these chemicals have been found to have beneficial pharmaceutical effects for humans, including compounds used in the treatment of human immunodeficiency, respiratory, cardiovascular, gastrointestinal diseases besides showing anti-inflammatory, antitumor, and antibiotic properties.
Sponges also provide a home for a number of small marine plants, which live in and around their pore systems. Symbiotic relationships with bacteria and algae have also been reported, in which the sponge provides its symbiont with support and protection and the symbiont provides the sponge with food. Some sponges (boring sponges) excavate the surface of corals and molluscs, sometimes causing significant degradation of reef substrata and death of the molluscs. The corals or molluscs are not eaten; rather, the sponge is probably seeking protection by chemically excavating into the hard structures it erodes. Even this process has some beneficial effects, in that it is an important part of the process by which bound calcium is recycled.

 


Niphates sp. (Niphatidae - 90kB)


Cinachyra schulzei (Tetillidae / Spirophorida - 100kB)


Aka sp. (Niphytidae / Haplosclerida - 90kB)