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Cervinia langi n. sp. and Pseudocervinia magna (Copepoda: Harpacticoida) from the Beaufort Sea (Alaska, U.S.A.)
(Transactions of the American Microscopy Society, 1979) Montagna, Paul A.
Two species of the family Cerviniidae have been collected from the Beaufort Sea off the coast of Alaska. Pseudocervinia magna (Smirnov, 1946) and Cervinia langi n. sp. were found in association. Lang (1936, 1948) described the new species as a variant of Cervinia synarthra Sars, 1911. However, C. langi is consistent and unique in the setation of its swimming legs and in details of the mandible and maxilliped. A key to the species and a table of salient morphological characters of the genus Cervinia are given. Appendages from the cephalothorax of P. magna are also figured, and its taxonomic position is discussed.
Two new bathyal species of Pseudotachidius (Copepoda: Harpacticoida) from the Beaufort Sea (Alaska, U.S.A.)
(Journal of Natural History, 1980) Montagna, Paul A.
During the summer of 1977, the Oregon State University Benthic Group participated in a USCGC GLACIER cruise off the northeastern coast of Alaska, U.S.A. Two new species of Harpacticoida (Copepoda) were found from several of the bathyal stations occupied. Pseudotachidius brevisetosus sp. nov. occurred in 15 samples from 4 stations. Pseudotachidius bipartitus sp. nov. co-occurred with P. brevisetosus in 5 samples from 3 stations. The areal extent was not great, hut the depth ranged from 659-1144 m for the 3 stations where both species occurred. A single P. brevisetosus female was found at the fourth station, where the depth was 403 m. Pseudotachidius bipartitus is .most similar to Pseudotachidius vikingus Drzycimski, but differs from it and other members of the genus in that the endopod of the first leg is 2-segmented. Pseudotachidius brevisetosus is most nearly related to Pseudotachidius coronatus T. Scott, but differs from it in the setal arrangement of the fourth and fifth legs, and most importantly in the transformed endoped of the male second legs. The setal arrangements ofP. coronatus and Pseudotachidius similis T. Scott are in question, due to differing interpretations of the original descriptions. A re- examination of the literature is discussed so that the relationships of the new species are clearly defined. All figures were made with the aid of a camera lucida. The nomenclature and descriptive terminology are adopted from Lang (1948, 1965) and Coull (1977). The following abbreviations are used throughout the text: R = rostrum, A 1 -- antennule, A 2 = antennae, Md = mandible, Mxl = maxillula, Mx = maxilla, Mxp = maxilliped, P1-P6 = legs 1-6, CR = caudal rami, GF = genital field, Bend. = baseoendopodite. Body length measurements are from the base of the R to the base of the CR, excluding both. CR L/W (=length to width ratio) is measured from the inner proximal edge to the inner distal edge for length, and at the widest points for width.
A New Species And A New Genus Of Cerviniidae (Copepoda: Harpacticoida) From The Beaufort Sea, With A Revision Of The Family
(Proceedings of the Biological Society of Washington, 1980) Montagna, Paul A.
Cercinia unisetosa n. sp. from the bathyal zone of the Beaufort Sea (Arctic Ocean) is unique in the Cervinia in that is possesses a reduced fifth leg, moderate length caudal rami, and only one seta on the bases of the mandible and the maxilliped. The discovery of the male of Pseudocervinia magna (Smirnov, 1946) proves that the species should be redesignated as a Cervinia as originally described. Expansicervinia glacieria n. gen, & n. sp. from the deep-sea of the same area proves to be unique in the Cerviniidae in three expansions; the ventral margins of second thoracic segment; the basal segment of the antennule; and the terminal endopodite of the second leg. The genus Stratiopontotes Soyer, 1970 is synonymized with Ameliotes Por, 1969. Keys to the genus Cervinia and the family Cerviniidae are presented.
Decomposition of Spartina alterniflora in different seasons and habitats of a Northern Massachusetts salt marsh, and a comparison with other Atlantic regions
(Estuaries, 1980-03) Montagna, Paul A.; Ruber, Ernest
Packets of freshly harvested liveSpartina alterniflora were placed on the marsh surface, in a tidal ditch, in a pool contacting sides and bottom, and in the center-bottom of the same pool in September 1972. Rates of loss were the same for all four sites through day 242. After that packets on the marsh surface decomposed slower. A second experiment was begun in July only at the marsh surface and pool side sites. These lost dry weight much more rapidly than packets started in September. Populations of bacteria, fungi, diatoms, flagellates, ciliates and nematodes within the packets peaked within 60 days then decreased proportionately with the loss of dry weight in packets through day 242. After this, bacterial numbers decreased more rapidly presumably in response to a qualitative change in the packet material. Populations of flagellates and ciliates also declined rapidly after day 300. This decline occurred in new packets at around this date as well. In a limited set of samples 12 taxa were analyzed for date or detritus-age dependent occurrence. Of these, eight were data dependent, two were dependent on packet age, and two could not be determined from the data.
Production of dominant emergent vegetation and of pool algae on a northern Massachusetts salt marsh
(Bulletin of the Torrey Botanical Club, 1981) Ruber, Ernest; Gillis, Gregory; Montagna, Paul A.
Cover frequency for the emergent vegetation of three representative sections of a salt marsh is presented. Annual production values are calculated using the ash-free dry weights of a series of harvests of standing live and dead crops, and estimating export or decomposition losses from the standing crops from data on litterbag-losses. Production values are provided for tall and dwarf Spartina alterniflora, S. patens, Distichlis spicata, Juncus Gerardi, Salicornia europaea, Typha angustifolia and Scirpus olneyi, the last two being based on end-of-season harvests only. These species account for from 88 to 96% of the emergent cover of these marsh sections. Salt marsh pool production and cover values are obtained and integrated for 8 months of the year. Such pools comprise from 0 to 26% of the sections studied. These data provide a baseline for studies of energy transfer in this marsh.
Morphological adaptation in the deep-sea benthic harpacticoid copepod family Cerviniidae
(Crustaceana, 1982) Montagna, Paul A.
Por (1964) suggested that deep-sea harpacticoids were adapted to an "epipelic way of life", by means of a "gradual elongation of limbs". To test this hypothesis I examined four closely related Arctic species to determine if such a predicted gradient of morphological characteristics exists with increasing depth. The deep-sea macrobenthos is highly diverse (Sanders & Hessler, 1969), and harpacticoid copepod assemblages follow this trend (Coull, 1972). Species and genera from the family Cerviniidae are often dominant members of deep-sea benthic copepod communities (Brodskaya, 1963; Por, 1964; Por, 1969; Coull, 1972; Dinet, 1977; Montagna & Carey, 1978). Thus, members of the Cerviniidae are especially good for testing hypotheses about the deep-sea. In general, deep-sea harpacticoids are found patchily distributed at cm and m scales (Thistle, 1978), in agreement with Jumar's (1975) ''grainmatching model". Disturbance/predation is probably also important in structuring these communities since harpacticoids are negatively correlated with the presence of sessile surface-deposit feeding polychaetes (Thistle, 1979). In this study I pro vide information about the nature of speciation in deep-sea harpacticoids.
The relationship between abundances of meiofauna and their suspected microbial food (diatoms and bacteria)
(Estuarine Coastal and Shelf Science, 2004-11-19) Montagna, Paul A.; Coull, Bruce C.; Herring, Teresa L.; Dudley, Bettye W.
Samples were taken bi-weekly for one year at a sand site and a mud site in the North Inlet Estuary, Georgetown, South Carolina, for meiofauna, their suspected microbial food (bacteria and diatoms), and associated physical factors. Linear regression techniques were used to correlate food abundance and physical factors with the density of meiofaunal taxa. At both sites diatoms positively correlated with meiofauna taxa, but bacteria did not. Physical factors were not correlated with meiofaunal or microbial abundances at the sand site. Whereas, at the mud site meiofauna and diatom abundances were positively correlated with the depth of the redox layer and inversely correlated with temperature. Peaks of meiofaunal abundance did not follow peaks of food abundance. Analysis of copepods at the species level indicated that taxa response was due to the response of the dominant species. Even though some correlations existed, this study suggests that copepod species and meiofauna at the gross taxonomic level do not respond to changes in potential food abundance. Physical factors apparently influence both meiofauna and diatoms in the same fashion. However, bacterial abundance was not positively correlated with any of the factors studied.
Competition for dissolved glucose between meiobenthos and sediment microbes
(Journal of Experimental Marine Biology and Ecology, 2003-03-31) Montagna, Paul A.
Meiobenthos, small invertebrates inhabiting the surface layers of marine sediments, can absorb dissolved organic matter (DOM). Experiments were performed to test if meiobenthos can compete with sediment microbes for uptake of small amounts of [14C]glucose. Meiofaunal glucose uptake rates were measured by themselves and in the presence of sediment microbes. Glucose uptake by meiofauna was not inhibited by the presence of bacteria, nor did it appear that bacterial uptake was inhibited by meiofauna. Thus, there was no direct or interference competition. Uptake rates by 1 cm3 of sediment (bacteria) were four orders of magnitude greater than those of individual meiofauna, but on a biomass specific basis, meiofaunal uptake was in the same range if not higher than that of sediment bacteria. Thus, the potential for indirect or resource competition exists. Since bacterial biomass dominated the system studied, uptake of glucose was dominated by bacteria. The results support the hypothesis that in natural sediments, where the biomass of bacteria is higher than that of meiofauna, heterotrophic uptake is primarily a microbial process. However, resource competition between meiofauna and bacteria for DOM in sediments probably exists where bacterial biomass is low relative to meiofaunal biomass.
Meiofauna and chlorophyll associated with Beggiatoa mats of a natural submarine petroleum seep
(Marine Environmental Research, 2003-04-01) Montagna, Paul A.; Spies, Robert B.
Previous studies at the Isla Vista oil seep have suggested that meiofauna, particularly nematodes, might be an important factor in explaining macrofaunal enrichment by making bacterial biomass available to the benthic food web. To explore this possibility, we analyzed meiofaunal abundance and microalgal pigments inside and just outside of bacterial mats at this natural oil seep. The bacterial mats occur where crude oil and natural gas are actively seeping out of the sediment; cores from within the mats contained a great deal of crude oil (up to 50 %). Meiofaunal abundances were the same in and out of the bacterial mats (averaging 1·-9 × 106 individuals m-2). However, dramatic changes in community structure were noticed. Harpacticoids made up 19 % of the fauna outside the mats but only 1 % inside. Pigment concentrations were also the same in both sites with phaeophytin dominating chlorophyll (120 compared to 29.8 mg m-2). The variance of both microalgal pigments and meiofauna was much greater inside than outside, suggesting that the bacterial mats are a more heterogeneous environment. Although the effect of crude oil toxicity is not clear, the high abundances of microbial and meiofaunal biomass support the hypothesis of benthic enrichment via microbes and meiofauna.
Reproductive success, xenobiotic contaminants and hepatic mixed-function oxidase (MFO) activity in Platichthys stellatus populations from San Francisco Bay
(Marine Environmental Research, 2003-04-01) Spies, Robert B.; Rice Jr, David W.; Montagna, Paul A.; Ireland, Robert R.
To identify some specific effects of organic contaminants on fisheries in an urbanized estuary we compared the reproductive success of starry flounder from San Francisco Bay with concentrations of tissue contaminants and hepatic mixed-function oxidase (MFO) activity. We found significantly lower (P < 0·05) sediment concentrations of total identified polynuclear aromatic hydrocarbons (PAHs) in the less urbanized San Pablo Bay (SP) area (Fig. 1) than in the more urbanized central bay (CB) stations (Table 1). For flounder in early gametogenesis (August and September) the SP fish (n = 20) had significantly lower (P < 0·01) liver concentrations of Aroclor 1260 (0·34 ± 0·14 μg/g) than those at the CB stations: Berkeley (BK, n = 20, 1·6 ± 1·6 μg/g); Oakland (OK, n = 16, 2·3 ± 2·8 μg/g); and Alameda (AL, n = 4, 2·2 ± 1 μg/g). A similar pattern existed for DDT concentrations: SP = 0·2 ± 0·16 μg/g; BK = 0·1 ± 0·34 μg/g; OK = 0·4 ± 0·53 μg/g; and AL = 0·4 ± 0·33 μg/g. Total PAHs in livers were as follows: SP = 0·14 μg/g; BK = 2·6 μg/g; OK = 1·4 μg/g; and AL = 14 μg/g. Although gonad index, liver index, and presence of fin rot are inversely related to aryl hydrocarbon hydroxylase (AHH) activity, healthy fish in a similar reproductive state have lower AHH activities in the SP area. For example, in August and September, 1984, mean AHH activities were as follows: SP = 203 ± 89, and CB = 355 ± 200 pmol 3-OH-B[a]P mg microsomal protein min. We found a log-linear relationship for AHH activity and its percent inhibition by 7,8-benzoflavone (10 -4m) and only a few fish from SP showed enhanced AHH activity after addition of 7,8-benzoflavone. This suggests that most of the starry flounder in San Francisco Bay are induced.
Partitioning radiolabeled thymidine uptake by bacteria and meiofauna using metabolic blocks and poisons in benthic feeding studies*
(Marine Biology, 1988) Montagna, Paul A.; Bauer, J. E.
Techniques exist which allow for the measurement of in situ grazing rates of meiobenthos on sedimentary bacteria and microalgae. Radiolabeled substrates are incorporated into microbes which serve as food for meiofauna and which themselves also become labeled during feeding. However, during in situ grazing experiments, meiofauna may become radiolabeled by a variety of non-feeding processes. Proper controls to correct for these extraneous routes of labeling have been developed in the present study. The use of [methyl-3H] thymidine (3HTdR) in studies of meiofaunal grazing on bacteria has two unique advantages: (1) it is incorporated only into prokaryotic macromolecules, and (2) bacterial incorporation of 3HTdR may be selectively blocked by several inhibitors which are non-toxic to meio faunal grazers. Coupled with formalin-killed control treat ments, the use of these inhibitors makes it possible to accu rately determine the partitioning of radiolabel into meiofauna during grazing into adsorptive, absorptive and grazing components. A saturated solution of nalidixic acid and 5'-deoxythymidine was found to be most effective in inhibiting water-column bacterial uptake and incorporation of 3HTdR, and had no toxic effects on meiofauna. The inhib itor was found to immediately block bacterial incorporation of 3HTdR and was as effective at 20% saturation as at 100%. The presence of sediment reduced the effectiveness of this inhibitor by 50%. Solutions of the inhibitor with excess undissolved material, however, completely blocked sediment bacterial uptake of 3HTdR. Employing these techniques during in situ grazing experiments showed that up to 83% of total meiofaunal uptake of 3H-label may be attributable to non-grazing processes. Experiments conducted in slurried sediments yielded grazing rates which were the same as those from intact cores. Furthermore, meiofaunal grazing rates on multiple food sources (e.g. bacteria and diatoms) may be determined synoptically by adding isotopically-distinct sub strates (e.g. 3HTdR and H14CO3) to the same experimental incubation.
Meiofauna dispersal near natural petroleum seeps in the Santa Barbara channel: A recolonization experiment
(Oil & Chemical Pollution, 2005-03-10) Palmer, Margaret A.; Montagna, Paul A.; Spies, Robert B.; Hardin, Dane
Studies on the response of fauna to natural disturbances indicate that disturbance events may be important in structuring marine benthic communities. Benthic populations in the Santa Barbara Channel off Isla Vista, California are regularly subjected to natural disturbances by chronic petroleum seepage in the area. It has been suggested that these populations show enhanced dispersal abilities when compared to populations that are not disturbance-adapted. Our study compared the rate of meiofaunal colonization into azoic sediment trays buried at an oil seep site with a nearby comparison site free of fresh oil. At the comparison site, for all taxa examined, meiofaunal abundances in the colonization trays did not reach ambient (surrounding sediments) levels at any time during the 23-h experiment. At the seep site, meiofaunal abundances in the trays reached ambient levels in 6 to 23 h, depending on taxa. Thus, the rate of meiofaunal colonization was faster at the seep site than at the comparison site. Enhanced susceptibility to passive transport or active water column entry by some species was most likely responsible for the enhanced colonization rate at the seep site.
Microbial biogeochemistry and heterotrophy in sediments of a marine hydrocarbon seep
(Limnology and Oceanography, 1989) Bauer, James E.; Montagna, Paul A.; Spies, Robert B.; Prieto, Maria C.; Hardin, Dane
Vertical profiles of sediment and pore-water constituents and rates of microbially mediated geochemical processes were determined in surficial sediments (0-7-cm depth) of three stations in and around Isla Vista hydrocarbon seep off Santa Barbara, California. Measurements were made of pore-water alkalinity (total and carbonate), pH, Eh, dissolved oxygen, sulfate, and sulfide, total sedimentary organic carbon (TOC) and nitrogen, ATP, sulfate reduction and dark bicarbonate uptake and incorporation, and oxygen flux across the sediment-water interface in benthic chambers. In general, alkalinity, pH, sulfide, TOC, ATP, and all rate processes were greatest in sediments of that station (A) with active seepage and decreased with increasing distance from the seep. Sulfate depletion and extremely low Eh values occurred in station A sediments. At a station (B) with lower seepage rates than station A, sedimentary and pore-water constituents and rate processes were intermediate those measured at station A and a station (C) without seepage. Pore-water and sedimentary constituents as well as oxygen flux were strongly correlated with total extractable sedimentary hydrocarbons (TEH) measured at each station and for each corresponding depth interval. All parameters exhibited seasonal differences that may have been temperature-dependent. The greater concentrations of TEH, sulfide, and alkalinity with increasing sedimentary depth indicate that seep sediments are a source of these constituents to the water column and a sink for 02 and S042-. The strong heterotrophic, and possibly chemoautotrophic, character of seep sediments resembles that of other organically enriched systems. The diagenesis of petroleum hydrocarbons is a function of the biogeochemical patterns and microbial heterotrophic activities in surficial sediment
Monitoring long-term effects of offshore oil and gas development along the Southern California outer continental shelf and slope: Background environmental conditions in the Santa Maria Basin
(Oil & Chemical Pollution, 2005-03-10) Hyland, Jeffrey; Hardin, Dane; Crecelius, Eric; Drake, David; Montagna, Paul A.; Steinhauer, Margarete
Potential environmental impacts of materials discharged from oil and gas development and production platforms off the coast of southern California (Santa Maria Basin) are being monitored during an ongoing, long-term (fiveyear) field program. The study combines hypothesis testing of platform effects with basic research on the structure and dynamics of the regional ecosystem over a time series encompassing both seasonal and repeated annual scales. Oceanographic features and processes that are being measured focus on the benthos and include biological community indices and species abundances for hard-bottom and soft-bottom (macroinfauna and meiofauna) assemblages; levels and distributions of trace metals and hydrocarbons in bottom sediments, suspended particulates, animal tissues, and pore waters; water currents and otherphysical-oceanographicfeatures; various sedimentological properties (sediment grain size, total organic carbon, shear strength, distribution of mineral types, radioisotope profiles, and degrees of sediment mixing as a result of bioturbation); sediment and pollutant-transport processes; and animal-sediment-pollutant interactions. Synoptic measurement of these different environmental variables over the extended sampling period provides an opportunity to examine long-term variability in the benthic environment with respect to both natural and anthropogenic causes. Efforts to distinguish between natural variability and low-level cumulative impacts of drilling are given special attention. Results obtained during the first two years of sampling provide a basis for beginning to understand environmental processes and relations important in detecting and interpreting any subsequent impacts caused by drilling activities in this complex and productive region of the California outer continental shelf and slope. Background chemical, physical, and biological data generated during this period demonstrate that impacts of discharges from oil and gas operations should be detectable, if they occur, and should be distinguishable from natural environmental variability. Small inputs of barium and petroleum hydrocarbons have been detected and appear to be associated with the minor drilling activities that have occurred in the area thus far, however, these initial inputs have not led to any noticeable biological impacts. These initial results are hopefully of value for two reasons: (1) in providing a summary of basic chemical, physical, and biological features of the benthic environment within the Santa Maria Basin; and (2) in presenting information on research strategies that should be considered in designing studies dealing with similar resource-management problems in other parts of the world.
The effect on freshwater inflow on macrobenthos in the Lavaca River delta and upper Lavaca Bay, Texas
(Contributions in Marine Science, 1991) Kalke, R.; Montagna, Paul A.
A two year study on the effects of freshwater inflow on macrobenthos at selected sites in the upper portion of the Lavaca River and Bay was conducted from November 1984 through August 1986. Lowest densities occurred in lakes, and highest densities occurred in creek deltas. Sediment grain size did not have a significant effect on spatial distributions. The first year of the study had higher inflow rates than the second year. Temporal changes of inflow had a larger effect on spatial variability, because freshwater species had extended ranges during the high-flow year. Temporal variation in the benthic community during the study was caused by population changes of low salinity species, and this was associated with high inflow rates during the first year. Freshwater inflow is apparently necessary to induce the recruitment oflow salinity species in the upper bay. Chironomid larvae and the polychaete, Hobsonia florida, increased in density approximately 4 weeks after an inflow event. In contrast, the mollusks, Mulinia lateralis and Macoma mitchelli, had increased densities during the low inflow period resulting in high benthic biomass. Streblospio benedicti, a surface deposit-filter feeder, and Mediomastus californiensis, a burrowing deposit-feeder, were also positively correlated with increasing salinity during low inflow periods. Chlorophyll-a concentration in the surface water increased with inflow, indicating primary production was stimulated by inflow, and then decreased with increased salinity and increased filter feeder biomass. Non-molluskan benthic biomass was similar during wet and dry periods, and had a positive relationship with chlorophyll-a concentration. The amount, timing, and inter-annual variation of inflow influence both the spatial and temporal abundance and biomass ofbenthic macrofauna.
Meiobenthic communities of the Santa Maria Basin on the California continental shelf
(Continental Shelf Research, 2003-04-04) Montagna, Paul A.
The Santa Maria Basin encompasses the bulk of the continental shelf off the central coast of California. Meiofauna communities on this shelf are very abundant. The average density of metazoa plus protozoans to a sediment depth of 10 cm was 4040 per 10 cm2. Metazoan meiofauna were restricted to the surface sediments, where 84% were found in the top 4 cm. Over a 3-year period the average density within the top 4 cm of sediment was 1910 per 10 cm2 in water depths of 90–410 m. At a depth of 565 m the density was much lower, 218 per 10 cm2. The decrease in density correlated with a decrease in dissolved oxygen with depth. The percent of fine sediments and total organic carbon (TOC) content increased with water depth, therefore clay and carbon content were inversely correlated with density. There appears to be a seasonal cycle of increasing densities in the autumn and winter and decreasing densities in the summer. This cycle could be related to the seasonal cycle of storms and upwelling, which contribute energy to the benthos. The community structure of harpacticoid copepods was very complex. There were 115 species among 371 samples, and about 100 were undescribed species. Community structure was homogeneous between 90 and 410 m, but very different at 565 m. These changes correlated with changes in depth and sediment texture. Harpacticoid diversity also decreased with water depth. A suite of three factors; decreasing oxygen concentration and sediment grain size, and increasing TOC content; correlated with decreasing population density with water depth and with decreasing latitude across the basin.
The effect of freshwater inflow on meiofaunal consumption of sediment bacteria and microphytobenthos in San Antonio Bay, Texas, U.S.A.
(Estuarine and Coastal Shelf Science, 2004-11-19) Montagna, Paul A.; Yoon, Won Bae
If meiofauna are food-limited then they should respond with increased feeding rates when microbial production is stimulated. River inflow into estuaries is a source of organic matter that can be limiting to bacterial production, and nutrients that might limit primary production. Therefore, inflow should stimulate microbial primary and secondary production, and eventually meiofauna grazing rates should increase as a functional response to increased food availability and quality. To determine if meiofauna grazing rates were affected by inflow, two replicate stations were sampled in the upper, river-dominated end, of San Antonio Bay and contrasted with two replicate stations at the lower end of the estuary. The experiments were performed three times. Water column nutrients and sediment organic matter were higher in the upper end of the estuary than in the lower end. Benthic primary production was 2·5 times higher in the upper end than in the lower end. Benthic metabolism (measured by oxygen consumption) was also higher in the upper end, but bacterial production (measured by thymidine uptake) was not significantly different between the two ends. Grazing rates were 3·5 times higher on bacteria, and 2·5 times higher on microalgae in the upper end of the estuary than in the lower end, confirming our hypothesis that inflow would stimulate grazing rates. Grazing rates were dominated by juvenile molluscs (temporary meiofauna) which accounted for 39% of the microalgae and 68% of the bacteria ingested by the community. Juvenile molluscs were most prevalent in the upper, fresh-water zone. Harpacticoid copepods and nematodes had higher grazing rates in the lower end of the estuary. Grazing rates were higher on microalgae than on bacteria: 4% of the microalgae were removed per hour, compared to only 1% of the bacteria. Grazing rates on microalgae were 2·6 times higher than productivity, indicating meiofauna might be food-limited. Grazing on bacteria was low, and production (based on oxygen metabolism) exceeded grazing; thus bacterial food is not apparently limiting. Freshwater inflow can affect meiobenthic community structure, stimulate microbial production, and stimulate feeding rates by small invertebrates that can benefit by the increase in microbial production.
Photosynthetic response of natural assemblages of marine benthic microalgae to short- and long-term variations of incident irradiance in Baffin Bay, Texas.
(Journal of Phycology, 1992-02) Blanchard, Gerard F.; Montagna, Paul A.
This study was designed to understand the high variability characterizing primary production rates of microphytobenthos. The photosynthetic efficiency (αB) and photosynthetic capacity (PBmax) of the microphytobenthos were measured at different times of the day on two different dates (8 May and 7 July 1990). In July, unusually low light conditions were caused by the development of a brown tide (chrysophytes). Both light-limited and light-saturated photosynthesis changed at hourly and monthly scales. There was a linear relationship between αB and PBmax, suggesting a common response to environmental factors [αB= 0.0075(±0.00063)·PBmax+ 0.00097(±0.0071), R2= 0.94]. Incident irradiance at the sediment-water interface was the primary physical factor that explained variability of both αB (84%) and PBmax (92%). Temperature had a negative but minor effect that explained an extra 8% and 2% of the variance, respectively. There was no diel rhythm of αB and PBmax and incident irradiance was regulated by wind-induced currents. Therefore, microphytobenthos photosynthesis seemed to be primarily controlled by wind events in Baffin Bay.
The effect of freshwater inflow on meiofaunal and macrofaunal populations in the Guadalupe and Nueces Estuaries, Texas
(Estuaries, 1992-09) Kalke, Richard D.; Montagna, Paul A.
Two estuaries with very different inflow characteristics were compared to test the hypothesis that benthic standing crops are enhanced by freshwater inflow. Assuming predation pressure is similar in both estuaries, this would imply that freshwater inflow enhances secondary production. The Guadalupe Estuary had 79 times more freshwater inflow than the Nueces Estuary, and a third of the salinity. The Guadalupe had higher macrofaunal densities and biomass than the Nueces, and both parameters increased with decreasing salinity within the Guadalupe Estuary. Macrofauna density increased with increasing salinity in the Nueces Estuary, due to invasion by marine species. However, meiofauna population size responds differently than macrofauna. Meiofaunal densities were higher in the low-inflow Nueces Estuary, and increased with increasing salinity in both estuaries. Macrofauna diversity increased with salinity, both within and between estuaries. The macrofauna response supports the hypothesis that increased freshwater inflow stimulates secondary production. A review of past benthic studies in these estuaries and the historical climatic patterns indicate that wet years with high inflow result in increased macrofaunal productivity. Since, macrofaunal diversity decreased with lower salinity both within and between the estuaries, the enhanced productivity is due to increases by freshwater and estuarine species that can tolerate low salinities. Increased macrofaunal densities are associated with decreasing meiofaunal densities. The latter result could be due to either increased macrofaunal competition with or predation on meiofauna, or a lack of low-salinity tolerance by meiofauna.
Initial burial and subsequent degradation of sedimented phytoplankton: relative impact of macro- and meiobenthos
(Journal of Experimental Marine Biology and Ecology, 2003-03-31) Webb, Donald G.; Montagna, Paul A.
The initial burial (transfer through the sediment-water interface) and subsequent degradation of sedimented phytoplankton was examined in the laboratory in sediments containing meiofauna, both with and without macrofauna, over a 10-day period. Burial and degradation were monitored by following changes in vertical profiles of Chl a and phaeopigments in sediment columns with and without an addition of senescent Skeletonema costatum Greville (Cleve) cells to the sediment surface. The macrofauna present in the cores consisted of a subsurface deposit-feeder assemblage typical of organically enriched habitats. Upon diatom addition, the visual redox potential discontinuity (RPD) rose to or near the sediment surface. Chl a and phaeopigment levels increased 6 and 3 days after diatom addition, respectively, with no difference in concentrations in the presence or absence of macrofauna. These increases appeared to be confined to the top 5 mm of sediment. Overall, phaeopigment concentrations were higher in cores containing macrofauna. A minimum of 83 % of the added Chl a was transferred through the sediment-water interface in 10 days. In organically enriched habitats, the initial burial and subsequent degradation of sedimented phytoplankton appears to be a process dominated by the meiofaunal and microbial communities, and unaffected by subsurface deposit-feeding macrofauna.

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