Teresa Radziejewska

Status of Biodiversity in the Baltic Sea

The brackish Baltic Sea hosts species of various origins and environmental tolerances. These immigrated to the sea 10,000 to 15,000 years ago or have been introduced to the area over the relatively recent history of the system. The Baltic Sea has only one known endemic species. While information on some abiotic parameters extends back as long as five centuries and first quantitative snapshot data on biota (on exploited fish populations) originate generally from the same time, international coordination of research began in the early twentieth century. Continuous, annual Baltic Sea-wide long-term datasets on several organism groups (plankton, benthos, fish) are generally available since the mid-1950s. Based on a variety of available data sources (published papers, reports, grey literature, unpublished data), the Baltic Sea, incl. Kattegat, hosts altogether at least 6,065 species, including at least 1,700 phytoplankton, 442 phytobenthos, at least 1,199 zooplankton, at least 569 meiozoobenthos, 1,476 macrozoobenthos, at least 380 vertebrate parasites, about 200 fish, 3 seal, and 83 bird species. In general, but not in all organism groups, high sub-regional total species richness is associated with elevated salinity. Although in comparison with fully marine areas the Baltic Sea supports fewer species, several facets of the systems diversity remain underexplored to this day, such as micro-organisms, foraminiferans, meiobenthos and parasites. In the future, climate change and its interactions with multiple anthropogenic forcings are likely to have major impacts on the Baltic biodiversity.

Biological responses to disturbance from simulated deep-sea polymetallic nodule mining

Commercial-scale mining for polymetallic nodules could have a major impact on the deep-sea environment, but the effects of these mining activities on deep-sea ecosystems are very poorly known. The first commercial test mining for polymetallic nodules was carried out in 1970. Since then a number of small-scale commercial test mining or scientific disturbance studies have been carried out. Here we evaluate changes in faunal densities and diversity of benthic communities measured in response to these 11 simulated or test nodule mining disturbances using meta-analysis techniques. We find that impacts are often severe immediately after mining, with major negative changes in density and diversity of most groups occurring. However, in some cases, the mobile fauna and small-sized fauna experienced less negative impacts over the longer term. At seven sites in the Pacific, multiple surveys assessed recovery in fauna over periods of up to 26 years. Almost all studies show some recovery in faunal density and diversity for meiofauna and mobile megafauna, often within one year. However, very few faunal groups return to baseline or control conditions after two decades. The effects of polymetallic nodule mining are likely to be long term. Our analyses show considerable negative biological effects of seafloor nodule mining, even at the small scale of test mining experiments, although there is variation in sensitivity amongst organisms of different sizes and functional groups, which have important implications for ecosystem responses. Unfortunately, many past studies have limitations that reduce their effectiveness in determining responses. We provide recommendations to improve future mining impact test studies. Further research to assess the effects of test-mining activities will inform ways to improve mining practices and guide effective environmental management of mining activities.

Responses of Deep‐Sea Meiobenthic Communities to Sediment Disturbance Simulating Effects of Polymetallic Nodule Mining

During a benthic impact experiment (BIE) carried out during 1995–1997 by the Interoceanmetal Joint Organization (IOM) at an abyssal site in the North-East Pacific, sediment disturbance mimicking that resulting from polymetallic nodule extraction was created with a specialised device (the Benthic Disturber). The effects of the disturbance on meiobenthic communities were assessed immediately after disturbance and 22 months later. A reduction in meiobenthos abundance, observed immediately following impact, was not significant; neither were changes in composition of the meiobenthos which was dominated by nematodes and harpacticoids. The lack of any significant numerical response is probably accounted for by the moderate degree of disturbance in this study, compared with other BIE-type experiments. On the other hand, statistically significant changes in both meiofauna abundance and vertical distribution profiles in the changed sediment within the Disturber tracks were recorded. After 22 months, a significant increase in overall meiobenthos abundance was detected in that part of the test site affected by increased resuspended sediment settlement and receiving natural phytodetrital inputs. Certain taxon-specific responses on the part of nematodes and harpacticoids were noted both immediately after the disturbance and 22 months later. They were explained by the effects of sediment physical reworking and responses to phytodetrital enrichment. The results presented should aid in developing experimental designs, on both temporal and spatial scales, of future deep-sea tests aimed at assessing the scale and consequences of man-made impacts.

Meiofauna and sediment chloroplastic pigments on the continental shelf off Louisiana, U.S.A.

Abstract Organic matter derived from phytoplankton blooms in the euphotic zone represents an important component of the flux of material to the bottom sediments. The relationship between the supply of phytodetritus to bottom sediments and the horizontal and vertical distribution of meiobenthos in the continental shelf of the Gulf of Mexico off the coast of Louisiana, U.S.A., was studied in February 1992. A total of 13 stations located in two areas was visited. One area (“off Mississippi” eight stations) was adjacent to the Mississippi River mouth and was directly influenced by the river plume, while the other (“off Cocodrie” five stations) was situated west of the Mississippi River mouth. The sediment chloroplastic pigment contents (Chl a and total pigments) were significantly higher off Mississippi, as were densities of harpacticoid copepods, while nematodes were significantly more abundant off Cocodrie. Vertical profiles of sediment pigments, harpacticoid, nematode, and total meiobenthic densities were also markedly different in the two areas. Densities of total meiobenthos, nematodes, and harpacticoids correlated significantly with the sediment total pigment and Chl a contents off Cocodrie, while no significant correlations were detected off Mississippi. This is an indication that meiofaunal abundances in the latter area, exposed to a constant supply of sedimenting organic matter, seem to be controlled by factors other than the abundance of phytodetritus as expressed by the sediment chloroplastic pigment content.

Climatic and hydrological controls over the zoobenthos in a southern Baltic coastal lagoon

In a four-year-long (1985–1988) study of macro- and meiobenthos of the Szczecin Lagoon, a eutrophic and polluted coastal water body directly connected with the southern Baltic Sea, peculiar interannual dynamics of variables related to abundance was observed. The interannual component of variability was stronger than fine-scale seasonal dynamics. The interannual variations followed a trend whereby abundance of meio- and macrobenthos as well as biomass of the latter was high in 1985, dropped in 1986 and 1987, and rose again in 1988. As the trend could not be explained by local environmental data, explanation was sought by invoking wider-scale climatic and hydrological processes. Data for severity of winters preceding each year of study as well as trends in atmospheric circulation patterns, wind regimes, river runoff characteristics, and near-bottom conductance (used as a proxy for seawater intrusions into the lagoon) were compared to seasonal anomalies in meiobenthic abundance as well as in macrobenthic abundance and biomass. The seasonal mean meiobenthic log abundance anomalies produced no significant correlation with any of the variables tested. In contrast, the seasonal mean log macrobenthos abundance and biomass anomalies were significantly negatively correlated with winter severity proxies (mean winter temperature and cold sum) and flow rate determined with time lags generally longer than one month. The results provide indication of differences in responses of meio- and macrobenthic communities to climatic (winter severity) and hydrological changes, the long-term effects being visible primarily within the macrobenthos. However, establishing sound causal relationships requires longer time-series of data.

Living on the pH Edge: Diatom Assemblages of Low-pH Lakes in Western Pomerania (NW Poland)

Diatom communities were studied in 2003 in three low-pH peatbog lakes in Western Pomerania (NW Poland); two of the lakes (LK and ZB) represented natural acid water bodies (NAWB), the third lake (LP) being least acid stressed. The three lakes differed markedly in their abiotic regimes, mainly on account of water pH in the two NAWBs being consistently below 5.0, while the pH range in the non-NAWB extended well into the alkaline part of the pH scale. In terms of all the important environmental variables studied (pH, conductivity, dissolved organic C, dissolved Si, dissolved P, nitrate and ammonia N), the three lakes followed an environmental gradient with LP on one end and ZB, a fully natural peatbog reservoir with high acidity, lower conductivity, higher upper limit of dissolved organic C and higher dissolved P contents and much lower dissolved Si contents, on the other. The study confirmed the general pattern of a low taxonomic richness in waterborne and bryophyte-associated diatom assemblages inhabiting low-pH habitats. The diatom assemblages differed between the three lakes and conformed to the environmental gradient. The LP assemblage (216 taxa), dominated by the common neutrophile Achnanthidium minutissimum, showed a preponderance of circumneutral and alkaliphilous taxa; the LK diatoms (15 taxa) represented mostly acidobiontic and acidophilous taxa, while the ZB assemblage (11 taxa) consisted predominantly of acidobionts. The study supplied information on the distribution of taxa having a high conservation value on the European scale. Important in the NAWBs were rare and endangered diatoms, primarily members of Eunotia, as well as Frustulia crassinervia. Their occurrence, coupled with other environmental and biotic characteristics of the lakes studied, makes the latter ideal candidates for conservation and protection.

Nematode communities inhabiting the soft deep-sea sediment in polymetallic nodule fields: do they differ from those in the nodule-free abyssal areas?

ABSTRACT This study addresses whether or not nematode assemblages inhabiting the soft sediment in abyssal nodule fields are unique and differ from those occurring in the nodule-free abyssal areas. This question is important for the evaluation of possible diversity losses caused by nodule mining operations. The analysis involved seven datasets at genus-level of nematode assemblages from three nodule-bearing abyssal areas in the Pacific (the Clarion-Clipperton Fracture Zone or CCFZ, and the Peru Basin) and the Indian Ocean (CIOB), and five datasets from nodule-free abyssal regions (the Atlantic Ocean). Only individuals identified to valid genera were used in the analysis. Overall, more than 20,000 nematode individuals from 90 samples were analysed. The analyses showed that the nematode communities in the nodule fields did differ from those in the nodule-free abyss. The nodule fields are characterized by a higher microhabitat heterogeneity, which resulted in a higher diversity of nematode communities inhabiting the nodule fields. However, one set of dominant taxa (Monhysteridae, Microlaimus, Acantholaimus, Theristus and Desmoscolex) was identical for both the nodule-bearing and nodule-free abyss, although some genera were strongly and significantly associated with either the nodule-free abyss (Microlaimus) or the nodule-bearing abyssal regions (Capsula). On the other hand, nematode assemblages at nodule-bearing and nodule-free sites within the nodule-bearing abyss proved to be similar at the genus level. This makes it possible for the nodule-free sites to serve as donors of colonizers for the mining-impacted nodule-bearing abyss. However, this suggestion has to be treated with caution, because the species-level differences have not been tested yet.

New indicator species in the Baltic zooplankton in 1972

The occurrence of zooplankton species, indicating a salinewater influx from the North Sea into the Baltic Sea in 1972, is described. Particular attention is paid to 8 species so far unknown in this region (Ectopleura dumortieri, Rosacea plicata, Tomopteris kefersteini, Aetideus armatus, Centropages typicus, Eucalanus elongatus, Metridia lucens, Electra pilosa). The appearance of these zooplankters in the Southern Baltic Sea is discussed in relation to the hhdrographic changes taking place in this area in 1972. Based on these data, assessments are made regarding the intensity of dynamic exchange processes in the Baltic and North Atlantic waters in 1972.

Meiobenthos of the Sub-equatorial North-Eastern Pacific Abyssal Seafloor: A Synopsis

The metazoan meiobenthos of the sub-equatorial North-Eastern Pacific abyss, CCFZ included, groups a fairly high number of higher taxa (including nematodes, harpacticoid copepods, ostracods, kinorhynchs, tardigrades, gastrotrichs, halacaroid mites, loriciferans, meiobenthos-sized polychaetes), the free-living nematodes and harpacticoid copepods being dominant. Both groups are very diverse in terms of taxon (genus, species) richness, the genus-level lists from the studies conducted so far containing 10–246 and 34–62 genera of nematodes and harpacticoids, respectively. Most genera (e.g. Acantholaimus among the nematodes and Pontostratoites among the harpacticoids) seem to occur throughout CCFZ, although the dominant genera change depending on the location (e.g. the Terschellingia nematodes were found to dominate in the eastern part of CCFZ and Acantholaimus in most other locations sampled). Most of the individuals found in samples represent as yet unknown, undescribed species. Meiobenthic abundances were found to vary over a range on the order of 101–102 ind./10 cm2, i.e. an order or two lower than the densities recorded in shallower and shelf waters. The variability in the abundance is thought to results from sediment- and habitat type-dependence (nodule-bearing versus nodule-free bottom, the nodules supporting characteristic faunas of their own) as well as from small-scale patchiness induced by natural factors (near-bottom water dynamics, activity of megafauna, presence of biogenic structures such as large protozoans the Xenophyophorea and the Komokiacea). The CCFZ meiobenthos was found to respond to episodic inputs of organic material in the form of phytodetritus sedimentation, some nematode (desmoscolecids) and harpacticoid (argestids) taxa being particularly responsive and increasing their abundance.

Characteristics of the Sub-equatorial North-Eastern Pacific Ocean’s Abyss, with a Particular Reference to the Clarion-Clipperton Fracture Zone

The deep seafloor, i.e. seabed areas at depths exceeding 800–1,300 m, cover about 88 % of the world ocean’s bottom. The most extensive areas represent the 3,000–6,000 depth range and include abyssal plains (depths > 4,000 m) the largest of which is the abyssal plain of the Pacific Ocean. The water column overlying it consists of a number of layers differing in their major characteristics. The most characteristic layers include that encompassing the oxygen minimum zone (OMZ, 100–1,000 m depth range in the Pacific) and the near-bottom layer, directly impinging on the seafloor. Once considered extremely stable, the near-bottom layer is now known to be prone to hydrodynamic effects such as tides and currents. The latter are generally weak, but periods of intensified current activity are not infrequent. The water column effects influencing the abyssal seafloor include also the transmission of the wind-generated surface physical energy down to the bottom (the “benthic storms”) on the one hand and sedimentation of surface-produced organic matter on the other. Both the benthic storms and organic matter deposition are known to be periodically, or episodically, intensified, thus contributing to natural environmental variability in the abyss. The Pacific abyssal plain sedimentary cover is mostly biogenic in origin. A characteristic part of the Pacific abyss is a huge (about 2 million km2) polymetallic nodule field within the NE sub-equatorial seafloor area experiencing low sedimentation rates and constrained by the Clarion and Clipperton fractures (the Clarion-Clipperton Fracture Zone, CCFZ). CCFZ extends sub-latitudinally along about 4,200 km, its surface inclining slightly westwards with depths in the east-west direction from about 4,000 to about 5,400 m. The seafloor, although generally flat, does show (particularly in the eastern part) distinct topographic features which are volcanic in origin. The relatively thin (50–200 m) sedimentary cover is formed by recent biogenic sediments (siliceous ooze). The major characteristic of the area is the presence of polymetallic nodule deposits. The nodules, occurring at abundances frequently exceeding 10 kg/m2, are mostly exposed on the sediment surface, but some are also embedded or buried in the sediment. The nodules, in addition to the occasionally occurring larger hard-rock fragments of cobalt-rich ferromanganese crusts, add to the deep-sea habitat heterogeneity and themselves constitute both a unique deep-sea habitat, of a great interest to marine ecologists, and an important mineral resource, of a great appeal to the marine mining community the size of which has been recently growing considerably.