Macrofaunal Biomass Research Articles

The benthic macroinvertebrates of the Block Island Sound

The benthic invertebrates of Block Island Sound have not been adequately studied, in contrast to other adjacent southern New England sounds. This study examines the species composition, abundance and biomass of benthic macrofaunal invertebrates at nine locations within Block Island Sound. The sites sampled, represent a wide range of subtidal habitats within the Sound, and were visited in February and September. Some 224 species were identified, of which almost half (104) were polychaetes. The benthic assemblages at most stations were dominated numerically by tube dwelling, surface detritus or suspension feeding amphipods, e.g. Ampelisca agassizi and A. vadorum, as well as the protobranch bivalve, Nucula proxima. This dominant Ampelisca-Nucula assemblage was associated with silty fine sand sediments. The average macrofaunal biomass for all stations was 158 g (wet weight) m −2, two thirds the average benthic biomass of Georges Bank, an important fishery area. Based on the examination of the records of earlier surveys in Block Island Sound, there is evidence that this silty-sand, ampeliscid-dominated assemblage has persisted since at least the mid-1940s.

Trophic structure and biomass distribution on two East Cape rocky shores

The distribution and biomass of macrofauna and macroalgae is described for two intertidal rocky shores near Port Elizabeth. The sheltered shore supported more macrofauna species (67) than the exposed shore (61), mainly owing to greater habitat heterogeneity; of 88 species recorded, 40 (46%) were shared. The shores had 13 and 23 macroalgal species respectively, with 9 shared. Ash-free dry biomass averaged 26 g m -2 over 200 m on the sheltered shore and 56 g m -2 over 80 m on the exposed shore for macrofauna and 81 g m -2 and 77 g m -2 for the algae. Lower animal biomass values on the sheltered shore may partly have been due to exploitation. Macrobenthic biomass was partitioned as follows on the sheltered and exposed shores respectively: grazers 86% and 82%, filter feeders 8% and 13%, carnivores 4% and 5% and deposit feeders 2% and 0%. Species warranting further study are listed.

The ecology of sandy beaches in Natal

Data from an ecological survey of four sandy beaches on the Natal coast of South Africa are presented. Physical parameters such as beach profile, particle size, moisture, Eh and carbonate content, as well as abundance, composition, biomass and distribution of both macrofauna and meiofauna were Investigated. A survey of the surf and swash zone mysids was also made. Natal beaches may be divided into two general types: (i) moderately exposed beaches of medium sand north of Blythdale with diverse meiofauna and typical sand beach macrofauna communities, and (ii) very exposed beaches of coarse sand south of Blythdale with true intertidal macrofauna often absent and a meiofauna dominated by large archiannelids.

The distribution of soil macrofauna on the west ridge of Gunung (Mount) Mulu, Sarawak.

The macrofauna of the soils on the west ridge of Gunung Mulu in 4th Division, Sarawak, were sampled during February and March 1978. The eleven sampling sites ranged from near the base of the mountain at 130 m a.s.1. to the summit at 2.376 m.Altitudinal changes from lowland rain forest (mixed dipterocarp forest) to lower montane and upper montane rain forests are concomitant with changes in soil from red yellow podzolics and regosols to peaty gley podzolics and organic peats.The abundance of the total macrofauna declined from 2,579 individuals m-2 at 130 m to 145 m-2 at 2,376 m. Declining population densities of ants and termites correlated significantly with increasing altitude but the effect on other groups was variable. Changes in total biomass were erratic and varied from 4.1-6.2 g m-2 (alc. w.w.) in the dipterocarp forest soils to 5.8 g m-2 in the lower montane, 9.3-20.2 g m-2 in the upper montane (tall facies) and 1.9-9.5 g m-2 in the upper montane (short and summit facies). Only the decline in the biomass of termites and ants correlated significantly with altitude. Other groups remained fairly constant, varied erratically or increased in the middle altitudes.The dipterocarp forest soil macrofaunal biomass was dominated by termites, beetles and earthworms (Megascolecidae and Moniligastridae), with ants the dominant predators. The lower montane forest was a transitional and ill-defined zone on the mountain and the soil macrofauna was also transitional to some extent. Termite biomass fell substantially and earthworms replaced them as the dominant detritivores, with beetles in a secondary role. Formicidae remained as the major predators. With the inception of peats in the upper montane forest (tall facies), the macrofauna was dominated by Coleoptera with earthworms, Diptera larvae and Blattodea in lesser roles. With increasing exposure in the upper montane forests (short and summit facies), several major groups disappeared altogether. The soils were dominated by Blattodea with Coleoptera and Megascolecidae of lesser importance. Chilopoda and Arachnida replaced Formicidae as the dominant predators.

A PRELIMINARY ANALYSIS OF BACTERIAL NUMBERS AND BIOMASS IN LANGEBAAN LAGOON

Summary Water samples taken down the length of Langebaan lagoon reveal a decline in bacterial numbers from Saldanha Bay to the head of the lagoon, with a parallel decline in suspended particles. Bacterial biomass (x 43, 27 mg.m−3) was comparable to zooplankton biomass. Intertidal samples from different sediment types showed an increase of bacteria towards the southern tip of the lagoon, with decrease in particle size and increases in percentage mud and percentage organic material. Bacteria comprise only a small percentage of the organic pool, but their biomass ranges from 16 to 232 mg (dry weight) per kg of wet sediment. This approximates a mean of 14,2 g (dry weight) per m2 (range 1,32 to 25,74): comparable to the biomass of benthic macrofauna. Considerable seasonal variation occurs in the organic pool.

Energy flow in the flora and meiofauna of sandy beaches

SynopsisInvestigation of a temperate and tropical beach has shown that, based on chlorophyllaanalyses, an epipsammic diatom population present in the temperate beach is absent in the tropical beach. Comparison of community respiration rates for the two beach populations excluding macrofaunal respiration shows that the tropical beach rates (which were constant over the period January-March) were about 9 times the winter rates of the temperate beach and about twice the summer rates. Annual microbial production is estimated at 15 gC/m2for the temperate beach and 72 gC/m2for the tropical beach. The greatly increased rate of production in the tropical beach was considered to be a function of increased water flow into that beach. In comparison, meiofauna and macrofauna biomass are less in the tropical beach and their respective production likely to be at most no more than in the temperate beach. It is proposed from experimental studies that the failure of animal populations fully to utilise microbial production in sandy beaches is due to the relative degree of exposure stripping significant quantities of microbial growth from this system. This proposal is discussed as a means of explaining mechanisms of control of animal production in sandy beaches.

Composition, Distribution, Abundance and Biomass of the Macrofauna and Meiofauna of Four Sandy Beaches

The macrofauna and meiofauna have been investigated quantitatively on four exposed sandy beaches of medium quartz sands. Of the 12 macrofauna species recorded, two bivalves (Donax spp.) and one gastropod (Bullia rhodostoma) made up the bulk of the numbers and biomass values on all beaches. Macrofauna biomass values were 0,01 - 316,46 g/m 2 on an ash-free, dry mass basis. Diversity index values for the macrofauna were low and on all beaches decreased from LW to HW irrespective of the distribution of densities. Similarity analysis indicated three fauna assemblages, which were less related to tidal heights than to quantities of available food. High meiofauna numbers were recorded (152 - 7056/10 cm 2 ) and these were made up mainly of crustaceans (48%) and nematodes (44%). Meiofauna ash-free dry biomass values were 0,08-3,36 g/m 2 . On all beaches the meiofauna tended to be concentrated at those tide levels where a moderate, but not extreme, degree of desiccation of the sand occurred. Biomass values of macrofauna and meiofauna were extrapolated to 1 m transects of beach giving macrofauna values of 17,5-16553,3 g/transect and meiofauna values of 13,8-76,0 g/transect. Production estimates based on these biomass values indicated that the meiofauna dominated two beaches and the macrofauna two beaches. Two general conclusions are discussed, namely that the meiofauna and macrofauna on these beaches are quite distinct faunal components in all respects, and that the meiofauna, although not part of the macrofauna food chain, are nevertheless of great quantitative importance in the flow of energy.

Biomass and production of a bivalve community on an intertidal mud-flat

Surveys of an intertidal mudflat in Southampton Water in two successive winters (1972 and 1973) yielded a total of 12 bivalve species, of which 5 contributed > 99 % of the biomass. The bivalve community is dominated by Cerastoderma edule (L.) (Biomass, B = 17–66 g ash-free dry wt m −2; Production, P = 20–71 g m −2 yr −1) and Mercenaria mercenaria (L.) ( B = 8–50 g m −2; P = 4–14 g m −2 yr −1), although Mytilus edulis L. ( B = 4–5 g m −2), Venerupis decussata (L.) ( B = 0.4 –2 g m −2) and Venerupis aurea (Gmelin) ( B = 0.6 –1 g m −2) are locally common. Total macrofaunal biomass (190 g m −2) and production (220 g m −2 yr −1) at Hamble appear to be higher than other comparable sites, although similar to mussel beds. The estimated transfer of bivalve biomass to predators (10.7 tonnes yr −1) and scavengers/decomposers (18.2 tonnes yr −1) shows the importance of the bivalve community to other trophic levels.

Energetic Aspects of the Intertidal Oyster Reef Community at Sapelo Island, Georgia (USA)

The total daily O_2 consumption rate of the intertidal oyster reef community in Georgia, USA was found to range between 0.6 x 104 and 5.0 x 104 mg O_2/m2 of reef surface, corresponding to a seasonal range of ambient water temperature from 9 degrees C to 30 degrees C. Oysters, nonoyster macrofauna, microbiota, and chemical oxidation were estimated to account for 48.1%, 10.0%, 21.9%, and 20.0%, respectively, of total O2 consumed. Reef macrofaunal biomass averages 1,108 g/m2 (ash—free dry weight) of which Crassostrea virginica comprises 87.5%. Growth of individual reef oysters, and, therefore, entire reefs, appears to be extremely slow, probably due to high maintenance costs and limited inundation time characteristic of the intertidal zone. The oyster reef community occupies only 0.06% of total marsh—water surface area in a salt marsh estuary unit (the Duplin River marsh—estuary system), but it can theoretically degrade 1% of the estimated excess annual net primary production in the system.

Dynamics and Energetics of Three Deposit‐Feeding Benthic Invertebrate Populations in Puget Sound, Washington

The dynamics and energetics of subpopulations of a numerically dominant deposit—feeding polychaete species, Pectinaria californiensis Hartman, were studied and compared with crude determinations of the same for the larger but rarer coexisting species of the same feeding mode, the heart urchin Brisaster latifrons (Agassiz) and the sea cucumber Molpadia intermedia (Ludwig). Monthly samples, taken for 1 yr at five stations in Puget Sound representing different habitats, were used in conjunction with laboratory measurements of respiration to assess the effects of seasonal and spatial variation in growth, mortality, and respiration on estimates of energy flow through these species populations. Pectinaria larval settlement (2,900—24,000 animals/m2) occurred at all locations in June 1970. Two of three age classes or cohorts were present simultaneously. Pectinaria represented 4%—26% of macrofaunal (> 1 mm) biomass, and 9%—47% of numbers at the five locations, based on the mean of four seasonal estimates. At the two stations where Brisaster and Molpadia coexisted with Pectinaria they contributed, respectively, 79% and 4% of macrofaunal biomass at one station and 13% and 63% at the other. Recruitment and growth of the two echinoderms appeared negligible, as neither numbers nor mean size changed during the study period. Annual production of Pectinaria, not including excretion or mucus production, varied 1.4—48 g C/m2°yr (14—49 kcal/m2°yr). The ratio of annual production to mean annual biomass, varying in the study area 3.3—5.5m provided a better estimate of turnover than the more commonly used ratio based on the lifetime of a cohort because of the difficulty of determining lifespan, a problem with most long—lived organisms. Pectinaria contributed 14%—42% of macrofaunal respiration in the area studied. But these numbers were shown to be affected by the failure to reproduce in the laboratory in situ oxygen—tension conditions. Such overestimates of population respiration from laboratory measurements were most marked for Brisaster and Molpadia. These latter estimates, while reflecting biomass data, unrealistically overshadowed the respiration of all other organisms. The sum of Pectinaria production and respiration (corrected for in situ oxygen tension) varied 2.6—9.2 g C/m2°yr (27—98 kcal/m2°yr), reflecting differences in rates of growth and mortality among stations. At two stations where primary production data were available, Pectinaria assimilated at least 1.3% and 3.3% of the carbon fixed by phytoplankton. Subsequently, 0.6% and 1.7%, respectively, were made available to predators and decomposers in the form of Pectinaria flesh. Because of its greater turnover of assimilated energy, Pectinaria contributed more to metabolic processes and to foodchain dynamics of the seabed than did the coexisting echinoderms. The echinoderms, on the other hand, may exert important influences on the structure of the community not accounted for in normal energetic assessments. Spatial and temporal variations in energy flow through species subpopulations can be large, and thus may limit the usefulness of a stability assumption in the development of predictive models for organic matter budgets.

On the importance of marine meiofauna for benthos communities.

1. In sublittoral sediments of silty sand live about 55000-1300000 meiofauna animals, which is a minimum figure because methods are not absolutely efficient. 2. Meiofauna biomass ranges from 0.2 to 2.0 g wet weight in sublittoral silty sand, that is about 3% of macrofauna biomass. 3. A higher percentage of meiofauna biomass is recorded from brackish water regions, intertidal beaches and from the deep sea, where meiofauna and macrofauna biomass are of the same magnitude. 4. Oxygen consumption in meiofauna animals is between 200 and 2000, in small macrofauna between 200 and 500, and in larger macrofauna between 10 and 100 mm3 O2/h/g wet weight. 5. The assumption is forwarded that in general meiofauna has a metabolism five times more active than that of macrofauna. 6. Generation time in meiofauna lasts from a few days as was observed in cultures, to one or a few years, as was observed in natural populations. For a generalization the guess is forwarded that three generations per year would be an average meiofauna value. 7. Life cycle turnover rate as calculated from life cycle models of two nematodes is 2.2-3. Multiplied by three annual generations results in an average annual turnover rate of about 9 for meiobenthos, which is about five times more than that in macrobenthos. 8. If one compares meiobenthos and macrobenthos, meiobenthos importance in terms of food consumed and in terms of biomass provided for the food chain is 15% in a community like sublittoral silty sand, although meiobenthos in terms of standing stock is just 3% of macrobenthos.

OXYGEN CONSUMPTION BY THE SEABED. II. IN SITU MEASUREMENTS TO A DEPTH OF 180 m1

Oxygen consumption by the seabed in Puget Sound was measured in situ in bell jars pushed into the bottom while monitored by television. Eleven stations were visited irregularly between January and August 1967. Depths ranged from 11 to 180 m, and sediment varied from coarse sand to mud. Observed short‐term rates were between 4 and 40 ml O2 m−2 hr−1 and were unrelated to depth (pressure), mean grain size, fine fraction of the sediment, organic matter or organic nitrogen in the upper 0.5 cm, or the biomass of macrofauna. Temperature accounted for only about 30% of the total variation in rates. We suggest that the seasonal changes of rates, and possibly the differences between stations, are caused primarily by changes of activity of small organisms as governed by the rate of supply of organic matter from the plankton. Estimates of annual rates of oxidation of organic matter on the seabed correspond to 17 and 25% of the phytoplankton production (14C uptake) near the stations in northern and southern Puget Sound, respectively.

Eine Bestimmungswethode für die radioaktiven Isotope 55 Fe und 59 Fe in Meerwasser : Kautsky, H. and D. E. Schmitt, 1962. Deutsch. Hydrogr. Z., 15 (5): 199–204

Low dissolved oxygen (hypoxia and/or anoxia) has become a major cause of change to the benthic component of ecosystems around the world. We present the response of a benthic community to hypoxia in organically enriched environments in Korean coastal waters. Disturbances due to low dissolved oxygen (DO), and organic enrichment altered community dynamics, result in defaunation during summer hypoxia with delayed recolonization occurring in winter. As DO decreased, the number of taxa, their abundance and biomass of macrofauna dropped significantly at inner bay stations in Chinhae Bay and Youngsan River estuarine bay affected by hypoxia. With the return of normoxic conditions in Chinhae Bay, recolonization was initiated by opportunistic species, with a 1–4 months lag. The polychaetes, Sigambra tentaculata, Mesochaetopterus sp., and Lumbrineris longifolia, were most persistent under hypoxia. The first recolonizers were the polychaetes Paraprionospio pinnata, S. tantaculata, Glycinde gurjanovae and Nectoneanthes multignatha and the bivalve Theora fragilis. The second group of colonizers included the polychaetes Capitella capitata, Mesochaetopterus sp. and L. longifolia, and the bivalve Raetellops pulchella. Hypoxic and near anoxic conditions resulted in mass mortality in Chinhae Bay and Youngsan River estuarine bay, but communities did partially recover after return to normoxic conditions despite delayed recolonization.