Scientific research topics 1995

1.) SEAGRASS IN THE GULF OF AQABA (RED SEA)
Paul Beyer, Christina Cepicka, Alexander Fuchs, Sylvia Hartl, Ulla Kail

Introduction
Seagrass meadows have been the subject of numerous studies in the last decades. The seagrass community in the Gulf of Aqaba is structurally and functionally complex. In general, the dominant species of seagrass is Halophila stipulacea, although Halophila ovale and Syringodium isoetifolium may co-occur or dominate in some areas. Seagrass species are adapted to thrive in low-nutrient, high-light environments, and seagrass meadows provide food, habitat, and nursery grounds for many vertebrate and invertebrate species. Prey species decrease their risk of predation by seeking shelter in the structure, that seagrass provides. The vegetative parts of the seagrass are used as substratum by a variety of benthic organisms. The leaves of the seagrass and the epiphytes provide food for fishes and crabs. A whole nutrient web is based on the existence of seagrass meadows. To survey this complex ecosystem, field research was carried out with the following objectives:
.) to establish a species list, containing the fauna occuring in the seagrass as well as he different species of seagrass itself.
.) to evaluate the biomass of the seagrass and the particle sizes of the sand in and near the seagrass.
.) to determine the most common epiphytic organisms.

2.) FEEDING BEHAVIOR OF MULLETS OF THE GENUS PARUPENEUS (MULLIDAE) IN THE GULFOF AQABA
Beate Gasser, Clemens Pausz, Susanne Scheiblauer

Introduction
The representatives of the family Mullidae are common fish species in coral reefs. Goatfishes are easily recognizable due to there elongate body and a pair of long barbels located under the lower jaw. These contain chemical sense organs and are used to search for food, "rooting" in the sand. When they are not being used, the barbels are withdrawn. All mullets are carnivorous and feed mainly on small invertebrates, even though some species also consume small fish. Goatfishes root in the sand, and are therefore an important ecological factor because they oxygenate the sediment. The food of the Mullidae consists of small individuals with low biomass. Therfore, a higher percentage of organic matter in the substrate makes rooting in the sand more effective, whereas a lower percentage would force the fishes to forage continuously. When goatfishes root in the substrate, other fishes may also feed on the exposed invertebrates. Because the mullets do not have any disadvantages from this relationship, this type of feeding community is termed commensalism.
This study deals with the following topics:
.) the substrate being fed on
.) differences in feeding behavior and food preferences of several species
.) dimensions ot the holes dug
.) the share of organic matter in the substrate
.) accompanying fishes.

3.) IN SITU OBSERVATION OF FISH CLEANING SYMBIOSIS IN THE GULF OF AQABA
Mark Hartl, Jürgen Herler, Thomas Reinthaler

Introduction
Our main interest was focused on the cleaner wrasse Labroides dimidiatus Cuvier & Valenciennes (1839), a very common fish of the family Labridae. L. dimidiatus is approximately 100 mm long, slender and is characterized by a light-blue base color with a median black stripe running from head to tail, ending in a 180° turn resembling a hook. The Pinna dorsalis covers the back beginning at the height of the P. pectorali' joint and ending and ending just before the tail base. P. ventralis is situated far towards the head, just behind the gill cover. P. analis is long, stretching from the tail base to the ventral midsection. These color patterns are assumed to inhibit aggressive behavior by potential predators. The mouth is set at the very apical end of the head in accordance with its feeding strategy.
Our objective was to seek L. dimidiatus, assess its territorial radius and to observe its behavior. In addition we aimed to integrate host behavior including cleaner tolerance, and the duration of the encounter observed.

4.) DISTRIBUTION AND AGGREGATIONS OF THE SEA-URCHINS DIADEMA SETOSUM AND ECHINOTHRIX CALAMARIS IN THE CORAL REEFS OF THE GULF OF AQABA
Maria Belegratis, Dehen Isman, Martin Ortner, Julia Walochnik

Introduction
This research was carried out in late October 1995 in the coral reefs of the Royal Diving Centre in the Gulf of Aqaba near the city of Aqaba, Jordan. The original plan was to investigate the density of both irregular and regular sea-urchins, but due to difficulties in locate the former, the research subject concentrated on regular sea-urchins. Due to the high density of Diadema setosum Leske (Diadematidae), this species was chosen to study the gregarious behavior during the daytime and the distribution along a transect on the reef.
The aggregations of Echinothrix calamaris Pallas (Diadematidae) in a seagrass meadow were also studied in order to observe the changes of sea-urchins aggregations on several successive days.

5.) THE MOVEMENT ACTIVITY OF THE SEA CUCUMBERS HOLOTHURIA ATRA AND STICHOPUS VARIEGATUS IN THE NATURAL HABITAT
Matthias Bruckner, Claudia Kohla, Petra Kraus, Lukas Pfeiffer

Introduction
The movement of the conspicuouscoral reef inhabiting sea cucumber Holothuria atra and Stichopus variegatus was investigated in a fringing reef of the Red Sea off Jordan in October 1995. To date, only a few studies have dealt with the population dynamic or ageing of Holothuroidea in the natural habitat. We not only measured the distances that these two species moved, but also analyzed their fecal pellets quantitatively. The goal was to obtain a rough impression of their secondary production. Analogous research on the influence of Mediterranean Holothuroidea on the metabolism of the sand was conducted by Amon & Herndl in 1991.
This study was designed to determine the best methods to mark the two species of Holothuroidea and follow their movements in the natural habitat. It should also demonstrate the rate of these epibenthic deposit feeders in the coral reef ecosystem.

6.) ENDOLITHIC FAUNA IN STONY CORALS
Thomas Hein, Christiane Todt

Introduction
The Gulf of Aqaba offers the marine biologist a colorful variety of stony corals. The different coral types are not only used by species living on the surface but also by animals living in the corals - the endolithic fauna. There is rich fauna in the calcareous corpus of the corals. These animals have evolved several strategies to find their final habitat:
.) drilling
.) juvenile forms have settled and waited till they were surrounded by parts of the coral
.) usind acids to resolve the coral
The aim of the present study was to compare different types of corals - dome-shaped, branched and a dead coralblocks in the same depth with regard to their endolithic fauna.
Has the morphology of the coral any influence on the species composition and abundance of the endolithic fauna?
In the sense of nature conservation we resigned to destroy the corals. In consequence we sampled and identified just species which have significant parts outside the coral and decided to take also attached species in account.