Biomass assessment of estuarine macrophytobenthos using aerial photography

Traditional approaches for biomass assessment of estuarine macrophytes over vast areas are time consuming. A methodology for quick and accurate biomass estimation of macrophytes, growing at intertidal mudflats, has been developed and verified. Using a calculated relation between biomass and colour densities on the aerial photographs, biomass of macrophytes over a large area (ca 900 ha) could be assessed with an accuracy of about 10%. Biomass estimates could be partitioned over seagrasses, various green algae and brown algae.Communication No. 330 Delta Institute for Hydrobiological Research, Yerseke, The Netherlands     

Effect of diurnal variations in natural irradiance on the apical length growth and light saturation of growth in five species of benthic macroalgae

The diurnal variation in apical length growth rate of five benthic macroalgae from the Swedish West Coast (Fucus spiralis L., F. vesiculosus L., F. serratus L., Ascophyllum nodosum (L.) Le Jolis, and Chondrus crispus Stackhouse) was measured during 1.5 to 2.0-h intervals for 3 to 5 d in September 1984. All species showed a maximum in growth rate in the morning, followed by a continuous decline throughout the rest of the day (most pronounced in F. serratus, A. nodosum and C. crispus). By comparing the growth rates with the average irradiance during the same interval, saturation irradiances for length growth in natural daylight regime were estimated; 60 to 70 Wm^-2 for F. spiralis and F. vesiculosus, 90 to 100 Wm^-2 for A. nodosum, 30 to 40 Wm^-2 for F. serratus and 10 to 20 Wm^-2 for C. crispus. Average growth rates during the dark hours ranged from 33% of average day growth rates in A. nodosum to 63% in C. crispus, respectively.     

Adaptation to low photon flux densities in Protogonyaulax tamarensis var. excavata,with reference to chloroplast photomorphogenesis

Changes in cellular chlorophyll content, cell volume, and light scatter of a New England red tide dinoflagellate, Protogonyaulax tamarensis var. excavata (clone GT-429), cultured in various light regimes are reported. Individual cells were analyzed, using flow cytometry and compared to traditional bulk measurements. Compared to high photon flux densities (182 Ein m^-2 s^-1), changes were measured that reflected increased chlorophyll fluorescence and increased cell volume at reducec photon flux densities when cell division was sustained, and increased flourescence and decreased cell volume when cell division ceased. These optical changes were accompanied by conformational changes in the chloroplasts. We found no change in photosynthetic carboxylating enzyme activities. We suggest that this photomorphogenesis of the chloroplasts at low photon flux densities may be an indication of stress and survival vs adaptive value to these persistent cells.     

Histological and histochemical changes in the gills of the yellowtail Seriola quinqueradiata exposed to the Raphidphycean flagellate Chattonella marina

The gills of the yellowtail Seriola quinqueradiata, exposed to Chattonella marina a red tide species, were examined histologically and histochemically. The pavement cells of primary lamellae were swollen in the exposed specimens. This presumably indicates that C. marina contains undetermined toxic substances. The number of mucous cells containing mucous decreased in proportion to the duration of exposure. The loss of the mucous substance in the cells is probably due to the ichthyotoxic stimulus caused by C. marina. A decrease of carbonic anhydrase activity in the secondary lamellae was confirmed, when mucous substances were lost in most mucous cells. Since the carbonic anhydrase usually exists in the epithelia of the secondary lamellae, it was presumably resolved by C. marina. The decrease of the carbonic anhydrase activity may cause certain physiological disadvantages to the fish exposed to C. marina.     

New development in the MOCNESS,an apparatus for sampling zooplankton and micronekton

Four variants of the Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) have been constructed to sample a broad size spectrum of oceanic animals from microzooplankton to micronekton. The systems differ in mouth opening dimensions (ranging from 1/4 to 20 m²), the number of nets carried (from 5 to 20), and the mesh size of the netting (from 64 m to 3.0 mm). A new electronics package enables an operator to send commands down a single conductor, armored cable to open/close the nets and provides 12-bit resolution for the environmental (temperature, depth, conductivity) and net operation data (flow, net-frame angle, net-bar release), which are transmitted up the cable to the deck unit at 2-s intervals. A microcomputer system, interfaced to the deck unit, calculates salinity, volume filtered by a net, net trajectory velocity, and vertical velocity. The data are printed out and stored on disc, and profiles of temperature and salinity versus depth are plotted during the course of the tow. Analysis of the relationship between the geometry of the MOCNESS under tow and the past and present methods used to estimate the water filtered by a net revealed that significant bias is introduced when the ascent or descent angle of a net is disregarded. The bias is a function of the ratio of vertical velocity to net trajectory velocity and results in an underestimate of volume filtered while shooting a net and an overestimate while hauling.     

Origin and nature of spermatophoric mass of the spiny lobster Panulirus homarus

In the spiny lobster Panulirus homarus (Linnaeus) the spermatophoric mass consists of a highly convoluted tube, containing the sperm mass and a gelatinous matrix. The spermatophoric components have their origin in the proximal vas deferens and the completed spermatophoric mass is stored within the distal dilated part of the vas deferens. In the proximal vas deferens the inner glandular epithelial cells give rise to leaf-like typhlosoles which gradually diminish in size and finally disappear in the distal vas deferens. The secretions originating from the typhlosole form the outer gelatinous matrix of the spermatophoric mass. Histochemical observations reveal that the wall of the spermatophore tube consists of neutral mucopolysaccharide, whereas the sperm mass and the gelatinous matrix are rich in acidic mucopolysaccharides. Both polyacrylamide gel electrophoresis and agarose gel electrophoresis were used to separate the acidic mucopolysaccharide (AMPS) complexed with the proteins and the simple proteins. In addition, AMPS have been isolated following the method of Rahemtulla and Lovtrup (1974) and used for electrophoresis. In both the polyacrylamide gel electrophoresis and agarose gel electrophoresis, the extracted acid mucopolysaccharides give only a single fraction which, in comparison with the standard acid mucopolysaccharides, corresponds to chondroitin sulphate. The functional significance of the chondroitin sulphate and neutral mucopolysaccharides in the spermatophoric components of P. homarus is discussed in relation to their functional role in spermatophore hardening and protection of the delicate spermatozoa during their prolonged storage on the sternum of the female.     

Ultrastructural alterations on chloride cells of the yellowtail Seriola quinqueradiata,following exposure to the red tide species Chattonella antiqua

By means of scanning and transmission electron microscopy, the influence of the red tide species Chattonella antiqua was examined with respect to the surface ultrastructures of chloride cells of the yellowtail Seriola quinqueradiata. Conspicuous ultrastructural alterations occurred on the apical surface of these cells. The majority of chloride cells in the control gills showed an apical surface with numerous cellular extensions, while more than half the chloride cells affected by red tide organisms exhibited an apical surface with fewer and smaller extensions, a wrinkled apical surface, or a protruded apical surface. These ultrastructural alterations of chloride cell surface may be due to the partial disturbance of salinity by C. antiqua, and reflect the changes of the ion-transport function in yellowtail gills exposed to red tide water.     

Nitrogen uptake and growth of the germlings and mature thalli of Fucus distichus

Fucus distichus L. was collected near Vancouver, Canada, in late fall and early winter, 1981. The effects of the forms of nitrogen (nitrate, ammonium or urea) and periodic exposure to air on growth, rhizoid development and nitrogen uptake in germlings was investigated. Gamete release, fertilization, germination and germling growth had no requirement for a specific form of nitrogen. Periodic exposure to air increased secondary rhizoid development twofold. Nitrate and ammonium uptake rates of the germlings were higher than for the mature thalli (20 to 40 times for nitrate and 8 times for ammonium), while the halfsaturation constant (K _s) values for nitrate were similar (1 to 5 M). The germlings showed saturable uptake kinetics but the mature thalli did not. When germlings were exposed to air it caused a 70% decrease in nitrate uptake, but not change in ammonium uptake. Ammonium uptake in the mature thalli was proportional to the ambient ammonium concentration. Nitrate uptake in the mature thalli appeared to follow saturation kinetics at low nitrate concentrations, but showed a non-saturable component at concentrations greater than 10 M. Presence of ammonium inhibited nitrate uptake by the mature plants but not by the germlings.     

In-situ measurements of nitrogenous nutrient uptake by kelp (Ecklonia maxima) and phytoplankton in a nitrate-rich upwelling environment

Nitrogen uptake by the kelp Ecklonia maxima Osbeck and phytoplankton was examined under different conditions of nutrient availability in a kelp bed off the Cape of Good Hope by measuring nutrient depletion in large plastic bags by the kelp and ¹⁵N uptake by phytoplankton. E. maxima took up nitrate and ammonia, but not urea, and showed only a weak preference for reduced nitrogen. Phytoplankton absorbed all three forms of nitrogen available, with a preference for ammonia and urea. Ambient nitrate concentration exhibited a marked and rapid decrease with northerly winds and an increase in response to offshore southerly winds. Nitrogen uptake by E. maxima was linearly related to ambient concentration and did not saturate even at nitrate concentrations >20g-at N l^-1, resulting in a significantly higher tissue nitrogen content under upwelling conditions. Nitrate imported by upwelling was the chief source of nitrogen utilised within the kelp bed. Locally regenerated nitrogen (ammonia and urea) was calculated to contribute only ca 4% of total nitrogen uptake during upwelling and 30% during the relaxation or downwelling phase.     

Availability of copper from phytoplankton and water for the bivalveMacoma balthica. II. Uptake and elimination from64Cu-labelled diatoms and water

The amount of copper taken up via algae and water byMacoma balthica from the Oosterschelde sea arm, S.W. Netherlands, was established using the radioisotope⁶⁴Cu. As far as we know, this isotope has never been used before in marine flod chain studies. As a model food source the marine diatomPhaeodactylum tricornutum was allowed to accumulate⁶⁴Cu for 1 d. These labelled algae were fed to the clams in the presence of the complexing agent EDTA (0.27mM). EDTA was added to prevent uptake of dissolved⁶⁴Cu that could be leaking from the labelled diatoms. In control experiments, unlabelled diatoms were fed toM. balthica in the presence of dissolved⁶⁴Cu (with and without EDTA) in order to assure a similar filtration activity. In repeated experiments with varying particulate/dissolved copper ratios, uptake through food always turned out to be at least as efficient as uptake from the water. It was concluded that Cu, associated with food, is well available for uptake byM. balthica.