Habitat loss and possible effects on local species richness in a species-poor system: a case study of southern Baltic Sea macrofauna

The effects of habitat loss on local species richness depend on the characteristics of the endangered system (including its total species pool and the distribution of species among the habitats). The present study focuses on the species-poor southern Baltic marine benthic biota. Macrobenthic samples were collected in three habitats: (1) soft bottom covered with vegetation; (2) stony reefs; (3) unvegetated sands. Fourty one percent of 54 observed macrozoobenthic species were habitat specific, while 30% occurred in all three habitats. There were no significant differences in total species richness among the three habitats. The accumulation curves plotted for subsets of data with selected habitats excluded lay below the curve plotted for the whole dataset, but only in one case the 95% confidence intervals of the subset curve did not overlap with those plotted for the whole dataset. The exclusion of samples from selected habitats produced a species richness drop ranging from 9 to 13%. The present study showed that habitat loss in a species-poor area with a relatively large ratio of generalist species cannot produce local species richness declines similar to those predicted for diverse marine systems. However, it must be emphasized that in species-poor systems, the loss of ecological function accompanying habitat loss could be disproportionally higher than that predicted based on decreases in species richness, as some functions are performed by a single species.     

Benthic macrofauna and sediments in the Severn Estuary

In the Severn Estuary and Bristol Channel, a multivariate analysis indicated eight groupings of macrobenthic fauna, each associated with a different physical habitat. Samples were faunistically impoverished, especially in sublittoral areas, but greater species richness was associated with reefs of Sabellaria alveolata , which extended well into the estuary.     

Reduplication in Slavic and Baltic: loss and renewal

The exposition comprises three parts. Part 1 surveys the Indo-European reduplication patterns (RPs) that have been lost in Slavic and Baltic: the languages show little or no evidence of inherited RPs in present and perfect formations, and in intensive verbs (Sect. 2.1), but some vestiges of reduplication in nouns can be identified (Sect. 2.2). Part 2 describes innovated RPs in the Slavic verb; they can be posited on the basis of scanty evidence that has survived the Late Common Slavic loss of coda obstruents. Part 3 describes Baltic innovations reflected in Lithuanian: reduplicative root formations (Sect. 4.1), several minor lexicalized RPs (Sect. 4.2.), and the para-lexical part of speech called eventives (Sect. 4.3). Their content categories, types of expression, patterns of iconicity, and grammatical function are analysed and exemplified in some detail. It is suggested that formations such as these may form the natural background for the creation of new patterns of morphological expression including patterns of reduplication.     

Recruitment response of methane-seep macrofauna to sulfide-rich sediments: An in situ experiment

Hydrodynamically unbiased colonization trays were deployed for 6 months (Oct. 2000 to April 2001) on the northern California margin (Eel R. region; 525 m) to examine macrofaunal colonization rates at methane seeps. The influence of sulfide on recruitment and survival was examined by deploying sediments with and without sulfide added; effect of seep proximity was evaluated by placing trays inside and outside seeps. The trays contained a two-layer system mimicking vesicomyid clam bed habitat geochemistry, with 8-9 mM sulfide in a lower agar layer at the start of the experiment. After 6 month on the seabed, the lower agar layer contained 2-4 mM H₂S. We observed rapid macrofaunal colonization equivalent to 50% of initial non-seep ambient densities. There was no difference in total colonizer densities, number of species, or rarefaction diversity among 3 treatments: (1) controls (no sulfide added) placed outside seeps, (2) trays with sulfide added placed outside seeps and (3) trays with sulfide added placed inside seep patches. Colonization trays with sulfide placed at seeps had different species composition from trays without sulfide place outside seeps; there were more amphipods (non-ampeliscid) and cumaceans in the seep/sulfide treatment and more nemerteans, Nephtys cornuta and tanaids in the non-seep/no-sulfide treatment. Outside seeps, annelids comprised < 15% of tray colonists; within seep patches, annelids comprised 5 of the top 10 dominant colonizing taxa (24% of the total). The polychaetes Mediomastus sp., Aphelochaeta sp., Paraonidae sp., and Nerillidae sp. exhibited significantly higher densities in sulfide additions. Tanaids, echinoderms, and N. cornuta exhibited sulfide avoidance. At least 6 dorvilleid polychaete species colonized the experiments. Of these, 4 species occurred exclusively in trays with sulfide added and 80% of all dorvilleid individuals were found in trays with sulfide placed inside seep sediments. Counts of large sulfur bacterial filaments were positively correlated with maximum sulfide concentration in each tray, and with proximity of sulfide to the sediment surface. However, total macrofaunal densities were not correlated with tray sulfide concentrations. As a group, tray assemblages achieved some but not all characteristics of ambient seep assemblages after 6-month exposure on the sea floor. Distinctive colonization patterns at methane seeps contribute to the dynamic mosaic of habitat patches that characterize the eastern Pacific continental margin.Overall, proximity of seep habitats had at least as great an influence on macrofaunal colonization as tray sulfide concentrations. Taxa characteristic of seep sediments were more likely to settle into trays placed inside rather than outside seep patches. Whether this is due to limited dispersal ability or local geochemical cues remains to be determined.     

Enhanced exoenzyme activities in sediments in the presence of deposit-feeding Chironomus riparius larvae

1. The combined effects of deposit‐feeding, bioturbation and bioirrigation by benthic macrofauna on the enzymatic hydrolysis of organic matter were studied in microcosms. Chironomus riparius larvae (Insecta, Diptera) served as model macrofauna and stinging nettle leaves (Urtica dioica) were used as a detrital food source. 2. In the upper 10 mm of the sediment (the habitat of C. riparius larvae), the activities of several exoenzymes, the contents of several fractions of particulate organic matter (POM), and the concentrations of dissolved oxidants (O₂, NO) were measured on a small scale. Fluorescent particles (luminophores) were used to quantify the vertical redistribution of particles within the same layer. 3. In control sediment, the addition of detrital food enhanced exoenzyme activities in the 0–2 mm layer only. In the presence of C. riparius larvae, exoenzyme activities increased to 10 mm depth. Further, the content of POM in the 0–2 mm layer was lower in the presence than in the absence of larvae, suggesting ingestion and subduction of the added detritus. After prolonged incubation without further food addition, exoenzyme activities returned close to background values in both treatments, whereas the vertical distribution of POM remained unchanged. 4. The overall penetration depth of O₂ and NO into the sediment was greater in the presence than the absence of C. riparius, the differences being more pronounced after prolonged incubation. Locally high O₂ and NO concentrations due to bioirrigation by C. riparius were measured deep in the sediment. Net downward transport of particles was observed only in the presence of C. riparius larvae and only at the beginning of the incubation. 5. I conclude that deposit‐feeding and bioturbation by macrofauna can quickly remove freshly deposited POM from the sediment surface and transfer it to less oxygenated sites (i.e. animal guts and deep sediment layers). Bioirrigation also increases the availability of oxidants deep in the sediment. The oscillation of oxidant supply to POM particles by ingestion–egestion, burial and re‐burial, and the intermittent bioirrigation of subsurface sediment, is probably the cause of the increased rate of organic matter hydrolysis, the rate‐limiting step in mineralization.     

Plant pigments and light penetration in intertidal sediments

Summary 1. Chromatographic analyses were used to determine the concentration of plant pigments in the sediments at four intertidal stations at Barnstable Harbor, Massachusetts, U.S.A. Two of the stations were sand flats exposed to relatively strong tidal currents and two were mud flats subject to weak currents. In general, highest concentrations of all pigments were found in the upper mm. Chlorophyll-a, chlorophyll-c and fucoxanthin concentrations decreased with depth but considerable quantities (20 to 50% of surface values) were found at 5 cm. Diatoxanthin, diadinoxanthin and carotene concentrations did not decrease with depth. Quantitative differences between the stations were noted.2. With one exception, measurements of light attenuation through these sediments, were roughly correlated with mean particle size.3. On one station, living diatoms were found as deep as 5 cm, but the vertical distribution of the pigments could not be explained by the diatom distribution.

---

Pflanzliche Pigmente und Lichtpenetration in Sedimenten des Gezeitenbereichs

Kurzfassung Die Verteilung pflanzlicher Pigmente und die Lichtpenetration wurden in vier verschiedenen Sedimenttypen untersucht, und zwar bei Barnstable Harbor, Massachusetts, USA. Mit einer Ausnahme erwies sich die Lichtattenuation als Funktion der Partikelgröße des Sediments. Obgleich lokale Unterschiede in der Pigmentverteilung an den einzelnen Untersuchungs-stationen beobachtet wurden, war das Verteilungsmuster grundsätzlich ähnlich. Die Konzentrationsmaxima lagen bei allen Pigmenten im obsersten Sedimentmillimeter. Die Konzentrationen der Chlorophylle und des Fucoxanthins verringerten sich allmählich mit zunehmender Tiefe; sie waren jedoch bei 5 cm Tiefe mit 20 bis 50% der Oberflächenwerte noch sehr hoch. Die Konzentrationen von Karotinen und anderen Xanthophyllen verringerten sich nicht mit der Tiefe. Die Verbreitung beweglicher pennater Diatomeen wurde an einer Station geprüft; es zeigte sich, daß die Mehrzahl der Individuen auf die obersten 3 mm beschränkt war. Lebende Diatomeen wurden bis zu einer Tiefe von 5 cm gefunden. Der Gehalt an organischer Substanz im Sediment wurde bestimmt und mögliche Korrelationen zwischen dessen prozentualem Pigmentanteil und einigen physikalischen Parametern der Stationen erörtert.

---

---

Contribution No. 90 Chesapeake Bay Institute, The Johns Hopkins University. Partially supported by the U. S. Atomic Energy Commission (Contract AT [30-1] 1477), and the Office of Naval Research (Contract Nonr 248 [54]) and NIH training grant 5 T1 GM 535-04.     

Sedimentation loss of phytoplankton cells from the mixed layer: effects of turbulence levels

In this paper, we describe a study of the role of turbulencein the loss by sedimentation of phytoplankton cells from themixed layer. The approach presented allows the quantificationof the sedimentation rate of phytoplankton in the whole rangeof turbulence levels of this layer. Two types of phytoplanktercan be distinguished according to the effect that turbulencecan exert on their sedimentation rate. The rate of those cellswhose settling velocity is lower than –1 m day^–1will not be modified by turbulence. The sedimentation rate ofcells with higher settling velocities can, however, be modifiedby the level of turbulence. A set of dimensionless numbers isgiven to delimit several processes that are important in thedynamics of phytoplankton sedimentation in a turbulent regime.The use of these dimensionless numbers suggests that an increasein the turbulence level in the mixed layer does not always implya decrease in the sedimentation rate of phytoplankton cells.     

The utilization of organic matter in shallow marine sediments by an epibenthic deposit-feeding holothurian

The utilization of organic matter and constituent food items in shallow marine sediments by Parastichopus parvimensis (Clark), an epibenthic deposit-feeding holothurian, has been investigated.Organic matter ingested from sediments of varying organic content was used by P. parvimensis with 22 % efficiency. In experiments with ¹⁴C labelled food all microorganisms associated with both plant detritus and decomposed matter of animal origin were used with over 40 % efficiency. Species of fresh brown, red, green, and blue-green algae were not assimilated. Detritus derived from the brown alga Dictyopteris zonarioides (Farlow) was used with a low efficiency while detritus from red and green algae was not assimilated. These results indicate that P. parvimensis does not utilize the large energy reserve available as plant detritus in near shore bottom habitats off Santa Catalina Island before to its decomposition by bacteria and fungi.     

Bacterial methanogenesis in holocene sediments of the Baltic sea

Microbial methanogenesis was proved geochemically, based on the abundance of methanogenic bacteria and methane production rates in experiments with radioactive carbon. The results are compared with direct measurements of methane concentrations in mud samples taken with a hermetic sampler. The migration of methane formed in sediments occurs during filtration of porewater rather than at the expense of gas diffusion.     

Grazing of bacteria and phytoplankton by heterotrophic nanoflagellates in a Baltic Sea sample

Grazing by heterotrophic nanoflagellates on bacteria and phytoplankton was studied in a laboratory experiment, using a natural pelagic community originating from the Tvärminne sea area off the southern coast of Finland. Water was prescreened to remove larger grazers. Four experimental treatments were used: light and dark, with and without added nutrients. The growth of the large heterotrophic flagellates was stimulated by increased production of < 3 m phytoplankton. Clearance rates for heterotrophic nanoflagellates were estimated and were found to be within the range of previously reported values.     

Breakdown of photosynthetic pigments and lipids in spinach leaves with ozone fumigation: Role of active oxygens

Dark-grown wheat leaves ( Triticum L. cv. Starke II Weibull) were illuminated repeatedly with light flashes giving partial phototransformation of protochlorophyllide to chlorophyllide. After short flashes (e.g. 15 ms red light, 250 W m⁻²), transforming only a minor part of the protochlorophyllide present, the first more stable chlorophyll(ide) measured ca 15 s after the phototransformation had its absorption maximum in the red around 672 nm. It stayed there during the following 30 min in darkness. After longer flashes (e.g. 125 ms), transforming a larger portion of the protochlorophyllide, the chlorophyll(ide) formed had its maximum absorption more towards 684 nm and shifted to 672 nm during a subsequent period in darkness. Thus, in this case a Shibata shift took place.
The conditions which produce the "stable" 672 nm form, without a Shibata shift, are discussed. The presence of large amounts of non-transformed protochlorophyllide remaining after the phototransformation seems to be important. Under such conditions it is possible that the Shibata shift is completed within a very short time.
Also the possible existence of two kinds of phototransformable protochlorophyllide is discussed. According to this idea one of the two protochlorophyllide forms produces a chlorophyllide absorbing at 672 nm shortly after phototransformation without having passed a Shibata shift. The other protochlorophyllide form photo-transforms to a chlorophyllide which proceeds through the Shibata shift.     

Steryl chlorin esters in sediments of the southern Baltic Sea

Sediments of the southern Baltic Sea were analysed for content of steryl chlorin esters, the chlorin compounds discovered recently in the marine environment. The chlorin esters occur in the Baltic sediments in substantial amounts and form a considerable fraction of the total chlorin content. Among the physicochemical parameters studied the highest correlation with the steryl chlorins showed organic carbon content in sediments and the content of fraction of sediments smaller than 10 μm. A significant correlation was observed between the steryl chlorins content and other chlorins as chlorophylla, phaeophytina, pyrophaeophytina as well as with β-carotene, the distinctly less significant correlation was with phaeophorbidea. This indicates an other way of formation of the steryl chlorins from algae than zooplankton grazing.     

Regional, vertical and seasonal distribution of phytoplankton and photosynthetic pigments in Lake Baikal

A 3-year phytoplankton study was carried out in Lake Baikal(Siberia) as part of the CONTINENT project and in conjunctionwith a 60-year long monitoring programme by the Irkutsk StateUniversity. A combination of microscopy and high performanceliquid chromatography (HPLC) pigment analysis was used. Allover the lake, the dominant functional group (by biovolume)was the vernal diatom blooms, due to the dominance of endemicCyclotella species. Chlorophyll a (Chl a) was significantlyhighest at the Selenga and Barguzin inflows (2.39 ± 0.34and 2.49 ± 0.18 nmol L^–1, mean ± 95% CI,respectively) and higher in the South than in the North (1.43± 0.26 and 0.96 ± 0.13 nmol L^–1). This variationof Chl a reflected changes in the phytoplankton composition.Diatoms and Chrysophyceae were the major contributors to thetotal Chl a except in the South (Chlorophyceae) and SelengaDelta (cyanobacterial picoplankton). There were also indicationsof species composition changes due to enhanced P-loading fromthe Selenga River. However, canonical analyses indicated thattemperature and stratification were the major driving forcesfor regional distribution patterns and seasonal succession.It seems likely that further global warming will cause a shiftin the species and group composition towards small cells atthe expense of the large endemic diatom flora.     

Density of Monoporeia affinis and biogeochemistry in Baltic Sea sediments

This study focused on effects from Monoporeia affinis reworking and ventilation activities on benthic fluxes and mineralization processes during a simulated bloom event. The importance of M. affinis density for benthic solute (O₂, ΣNO₂⁻ + NO₃⁻, NH₄⁺ and HPO₄²⁻) fluxes and sediment reactivity (mobilization of NH₄⁺ and HPO₄²⁻) following additions of organic material to the sediment surface was experimentally investigated using sediment-water and closed sediment (jar) incubations. Three different densities of M. affinis were used to resemble a low, medium and high density situation (1300, 2500 and 6400 ind. m^− 2, respectively) of a natural amphipod community. The degradation of phytodetritus (Tetraselmis sp., 5 g C m^− 2) added to the sediment surface was followed over a period of 20 days. Benthic solute fluxes of O₂, ΣNO₂⁻ + NO₃⁻ and NH₄⁺ were generally progressively stimulated with increasing number of M. affinis, while no such correlation was found for HPO₄²⁻. Solute fluxes were initially enhanced 1 to 2 days after the addition of phytodetritius, caused by mineralization of the most labile organic material and a food-stimulated irrigation by the amphipods. There was no effect from the activity of M. affinis on total denitrification (Dtot = Dn + Dw) or denitrification utilizing nitrate from coupled nitrification/denitrification (Dn) for any of the densities examined. Denitrification utilizing overlying water nitrate (Dw) was only about 10% of Dtot. Dw was significantly enhanced for the highest M. affinis density investigated. The reactivity of the sediment decreased progressively with increasing density of M. affinis and with time of the experiment. However, enhanced ammonium production at least 6 days after the organic addition indicated excretion of N-containing organic compounds by M. affinis. In conclusion, large spatial and temporal variations in density of M. affinis may be of significant importance for benthic solute fluxes and overall mineralization of organic material in Baltic Sea sediments.     

Unattended monitoring of potentially toxic phytoplankton species in the Baltic Sea in 1993

Variabilities in chlorophyll a fluorescence, temperature andsalinity in the surface were recorded unattended on board twomerchant ships in the Baltic Sea. When these recordings werecomplemented by automated water sampling, it was possible toanalyze the phytoplankton species composition in 426 samples.In total, 22 potentially toxic phytoplankton species or generawere detected. Nodularia spumigena was the only species thatformed extensive blooms The system has proved to be an effectiveearly warning method for exceptional and eventually harmfulalgal blooms. The possibilities for using this method as analternative, or a complement, to conventional methods in marinephytoplankton monitoring are discussed.     

Distribution of phytoplankton pigments in nine European estuaries and implications for an estuarine typology

Phytoplankton pigments were studied by LiquidChromatography (HPLC) in nine West Europeanestuaries. Three estuaries, i.e. the Rhine,Scheldt and the Gironde were sampled four timesto cover the different seasons, whereas theother six estuaries were sampled once. Pigmentdistributions in estuaries reflect bothriverine inputs as well as autochthonousblooms. Fucoxanthin was the most commonaccessory photosynthetic pigment showing thatDiatoms were the most common group in thestudied estuaries and were particularlydominant during autumn and winter. In the veryturbid Gironde estuary, degradation processeswere predominant between salinities 1 and 20,while Diatoms, Dinoflagellates and Cryptophytesbloomed above 20 salinity during spring andsummer. This contrasted with the highlyeutrophic but less turbid Scheldt, wherephytoplanktonic blooms occurred at lowsalinities close to the city of Antwerp. In theScheldt, we observed both a tenfold fluctuationof phytoplankton biomass and a fluctuatingpigment diversity index. In contrast,chlorophyll a was always low in theGironde, but we observed large variations ofpigment diversity among samplings duringdifferent seasons. Distribution of pheopigmentsshowed that the maximum turbidity zone (MTZ)was a highly reactive region for heterotrophicphytoplankton degradation. The Scheldt and theThames were the most anthropogenic influencedestuaries contrasting with the Gironde estuarythat has a less urbanised watershed. Anestuarine typology is proposed based on threeclusters emerging from a correspondenceanalysis of pigment variables and variablescharacterising the anthropogenic impact andphysical forcing.     

Spatial heterogeneity and dynamics of vernal phytoplankton species in the Baltic Sea in April-May 1986

The mesoscale phytoplankton distribution was studied as partof an international joint Baltic Sea Patchiness Experiment (PEX'86)during April–May 1986 in the open Baltic Proper. The studyperiod covered the peak phase of the phytoplankton spring bloom.The spatio-temporal dynamics of four dominating phytoplanktonspecies, Achnanthes taeniata, Chaetoceros spp., Skeletonemacostatum and Thalassiosira levanderi were studied within anarea of 20x40 nmi with grids of 2 and 4 nmi spatial resolution.The results showed highly varying spatial distributions forall species, and the variability was accentuated on the synopticspace scale before the development of the seasonal thermocline.The maxima of Chaetoceros spp. and Thalassiosira levanderi coincidedwith the anticyclonic and cyclonic eddies prevailing in thearea. Skeletonema costatum was found in high abundances onlywithin a warmer water mass of higher salinity advecting intothe area. The results pointed out that different successionalstages can simultaneously be found even in adjacent water massesand both the phytoplankton growth and composition during thebloom peak phase in the Central Baltic depend on complex factors,mainly those connected with mesoscale hydrodynamic features(eddies, frontal zones, jet currents).