Petra Heinz

RESPONSE OF DEEP-SEA BENTHIC FORAMINIFERA FROM THE MEDITERRANEAN SEA TO SIMULATED PHYTOPLANKTON PULSES UNDER LABORATORY CONDITIONS

Food and oxygen concentrations have been identified as environmental constraints influencing the vertical distribution of benthic foraminifera. Field studies, however, have been largely inconclusive as to which degree each factor regulates the observed distribution pattern. For this reason, different experiments were performed to investigate the response of deep-sea benthic foraminifera to simulated phytodetritus pulses under laboratory conditions, where oxygen concentrations can be influenced separately. In the laboratory, deep-sea foraminifera developed a normal vertical distribution pattern, and the habitats of single species reflected the results obtained from field investigations. Therefore, conclusions from the data produced in the laboratory can be transferred to nature. A mainly epifaunal life style was shown for Adercotryma glomerata and Spiroplectinella earlandi, but also indicated for Uvigerina peregrina. Hippocrepina sp. was spread over the entire sediment column with a shallow infaunal maximum. Epistominella pusilla, Seabrookia earlandi and Alveolophragmium wiesneri showed an epifaunal to shallow infaunal distribution. Ceratobulimina arctica, Trochammina inflata and Melonis barleeanum preferred an infaunal habitat. No suspension feeders were observed in the experiments. The addition of algae as food material resulted in elevated population densities. Under the influence of high oxygen contents with no or only short-term fluctuations, no migration to the upper layers was recorded after the addition of food. However, more specimens were found in deeper layers, because more organic material was transported downward into the sediment after the food pulse. The experimental laboratory results support the theoretical scenarios outlined in the TROX-model.

Time-response of cultured deep-sea benthic foraminifera to different algal diets

The vertical distribution of benthic foraminifera in the surface sediment is influenced by environmental factors, mainly by food and oxygen supply. An experiment of three different time series was performed to investigate the response of deep-sea benthic foraminifera to simulated phytodetritus pulses under stable oxygen concentrations. Each series was fed constantly with one distinct algal species in equivalent amounts. The temporal reactions of the benthic foraminifera with regard to the vertical distribution in the sediment, the total number, and the species composition were observed and compared within the three series. Additionally, oxygen contents and bacterial cell numbers were measured to ensure that these factors were invariable and did not influence foraminiferal communities. The addition of algae leads to higher population densities 21 days after food was added. Higher numbers of individuals were probably caused by higher organic levels, which in turn induced reproduction. A stronger response is found after feeding with Amphiprora sp. and Pyramimonas sp., compared to Dunaliella tertiolecta. At a constant high oxygen supply, no migration to upper layers was observed after food addition, and more individuals were found in deeper layers. The laboratory results thus agree with the predictions of the TROX-model. An epifaunal microhabitat preference was shown for Adercotryma glomerata. Hippocrepina sp. was spread over the entire sediment depth with a shallow infaunal maximum. Melonis barleeanum preferred a deeper infaunal habitat. Bacterial cell concentrations were stable during the laboratory experiments and showed no significant response to higher organic fluxes.

BEHAVIOR AND RESPONSE OF DEEP-SEA BENTHIC FORAMINIFERA TO FRESHLY SUPPLIED ORGANIC MATTER: A LABORATORY FEEDING EXPERIMENT IN MICROCOSM ENVIRONMENTS

The behavior of deep-sea benthic foraminifera in response to seasonal inputs of food material was examined through feeding experiments. The experiments using sediments from Sagami Bay (1425 m water depth) containing living foraminifera were carried out using microcosms (aquaria) with thin-walled glass sides. Three different nutrient levels were tested in order to observe how benthic foraminifera reacted to deposited organic matter. Observations of both behavior and microhabitat segregation with respect to the sediment-water interface were conducted using a sideways-mounted binocular microscope. Benthic foraminifera were vertically distributed according to three types of microhabitat segregation patterns, comparable to those of natural populations in Sagami Bay: shallow infaunal, intermediate infaunal and deep infaunal. After addition of food into the aquaria, many foraminifera migrated upwards to a shallower part of the sediment and some foraminifera ingested food. Shallow and intermediate infaunal species reacted faster to newly deposited food materials than deep infaunal species. Among deep infaunal species, Globobulimina affinis reacted very slowly to added food, whereas Chilostomella ovoidea did not respond at all. Reactions to newly deposited organic matter observed in this experiment vary from one microhabitat to another. These different food preferences are an important factor for understanding foraminiferal microhabitats and the degradation of phytodetritus. The size distribution of foraminiferal tests after the experiment was completed suggests that some species reproduced during the experimental run, although there was no significant difference in total numbers of foraminifera between fed and unfed aquaria. Our results indicate that some benthic foraminifera may reproduce in response to organic matter arriving before the spring bloom.

Laboratory observations of benthic foraminiferal cysts

Long-term observations on living benthic foraminifera in the laboratory were performed to investigate their behaviour and life style. We noticed that the formation of cysts or sedimentary envelopes is a common feature within many groups of foraminifera (organic walled, agglutinated and calcareous) in the laboratory. Several kinds of cyst were observed. In most cases, the entire foraminiferal shell was canopied with detritus or particles, but some specimens covered only parts of their body, such as the aperture region or pseudopods. Cysts were found attached to the glass walls of culture vessels or free in and on the sediment. Foraminifera stayed within cysts for hours to weeks. After leaving sedimentary envelopes, some specimens immediately started to build new ones, others not. The function of cyst formation observed in the present study was not clear, except one case where reproduction took place. Some monitored structures seemed not to be sedimentary cysts but unilocular agglutinated foraminifera with probably allogromiid-like organization. The formation of sedimentary envelopes seems to be a very basic character of foraminifera, suggesting a mechanism for the evolution of shells.

70 kD stress protein (Hsp70) analysis in living shallow-water benthic foraminifera

Abstract Hsp70 is a phylogenetically highly conserved protein family present in all eukaryotic organisms tested so far. Its synthesis is induced by proteotoxic stress. The detection of Hsp70 in foraminifera is presented here for the first time. We introduce a standard immunoblotting protocol modified for the detection of Hsp70 in shallow-water benthic foraminifera. Additionally, we showed a temperature-dependent expression pattern of Hsp70 in Ammonia tepida.

Ecological and Biological Response of Benthic Foraminifera Under Oxygen-Depleted Conditions: Evidence from Laboratory Approaches

Laboratory experiments are a valuable way to elucidate physiological and ecological processes of benthic foraminifera under oxygen-depleted conditions. Experimentally tested survival rates and other experiments show high tolerance of many species under low oxic to anoxic conditions. Laboratory observations raised different assumptions to explain the physiological adaptations to this tolerance. Denitrification processes seem to be one important mechanism. Nevertheless, foraminifera try to colonize sediment horizons with optimal species-specific oxygen concentrations. Experimental settings demonstrated the importance of oxygen gradients for the orientation in sediments. At the same time, foraminifera change the oxygen concentration in their microenvironment by respiration. Despite high bioturbation, they do not appear to influence the flux of oxygen into the sediment. Experimental working in oxygen-depleted environments needs a reliable determination of living foraminifera during the experiment, e.g., different biochemical techniques. Additionally, electrochemical or optical oxygen sensors that measure the oxygen concentration are necessary.

METHODS AND APPLICATIONS IN MICROPALAEONTOLOGY

Micropaleontology continues to evolve into a broad and methodologically diverse field. Since the day has only 24 hours, reviews and occasional state-of-the-art syntheses are increasingly important to catch up with the latest developments. Like many practitioners of the science watching the scene, we could not to fail to notice the appearance of a new book entitled “Methods and Applications in Micropaleontology”. The title of the book immediately awakened our curiosity. A comprehensive dedicated tome with such content is long overdue, since existing works either treat methods only in passing or are desperately outdated. Could this be the much-needed, up-to-date synthesis? A closer inspection soon revealed that the authors forgot to add the phrase “selected studies in.” This book is a collection of individual papers, not a comprehensive review. Nevertheless, this should not distract us from considering the …

METHODS AND APPLICATIONS IN MICROPALAEONTOLOGY: Edited By J. Tyszka, M. Oliwkiewicz-Miklasińska, P. Gedl and M. A. Kaminski, 2005, Studia Geologica Polonica, v. 124, Polska Akademia Nauk, Poland, 410 pp; ISBN: 83-918081-4-9; List price: €30.00 or

Micropaleontology continues to evolve into a broad and methodologically diverse field. Since the day has only 24 hours, reviews and occasional state-of-the-art syntheses are increasingly important to catch up with the latest developments. Like many practitioners of the science watching the scene, we could not to fail to notice the appearance of a new book entitled “Methods and Applications in Micropaleontology”. The title of the book immediately awakened our curiosity. A comprehensive dedicated tome with such content is long overdue, since existing works either treat methods only in passing or are desperately outdated. Could this be the much-needed, up-to-date synthesis? A closer inspection soon revealed that the authors forgot to add the phrase “selected studies in.” This book is a collection of individual papers, not a comprehensive review. Nevertheless, this should not distract us from considering the …

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Micropaleontology continues to evolve into a broad and methodologically diverse field. Since the day has only 24 hours, reviews and occasional state-of-the-art syntheses are increasingly important to catch up with the latest developments. Like many practitioners of the science watching the scene, we could not to fail to notice the appearance of a new book entitled “Methods and Applications in Micropaleontology”. The title of the book immediately awakened our curiosity. A comprehensive dedicated tome with such content is long overdue, since existing works either treat methods only in passing or are desperately outdated. Could this be the much-needed, up-to-date synthesis? A closer inspection soon revealed that the authors forgot to add the phrase “selected studies in.” This book is a collection of individual papers, not a comprehensive review. Nevertheless, this should not distract us from considering the …