Varying growth rates in bamboo corals: sclerochronology and radiocarbon dating of a mid-Holocene deep-water gorgonian skeleton (<Emphasis Type=Italic>Keratoisis</Emphasis> sp<Emphasis Type=Italic>.</Emphasis>: Octocorallia) from Chatham Rise (New Zealand)

A branched mid-Holocene bamboo coral skeleton of the isidid gorgonian genus Keratoisis (Octocorallia) recovered at southwestern Chatham Rise (New Zealand) from an average water depth of 680 m is described with respect to sclerochronology and age determination. Growth rates of the Mg-calcitic internodal increments were investigated by the counting of colour bands and radiocarbon dating. Growth banding is produced by varying orientations of crystal fan bundles towards the image plane. The skeleton shows three growth interruptions, which are documented in all branches. AMS ¹⁴C ages decrease from base to top of the trunk and from the central axes to the margins of the branches, documenting a simultaneous vertical and lateral growth. The data provide a maximum age of 3,975 ± 35 years BP, and a record spanning 240 ± 35 years. While calculated longitudinal growth rates amount to an average of 5 mm year⁻¹ during a 55-year record, average lateral linear extension rates of 0.4 mm year⁻¹ are an order of magnitude lower, still allowing for a seasonal to annual resolution of colour bands on a macroscopic scale and for a daily to monthly resolution on microscales of individual crystal generations to fascicle bundles. Hence, the isidid skeleton provides a high-resolution archive of paleoceanographic dynamics in deeper water masses. Concentric incremental accretion around the central axis in the early growth stages changed into a unilaterally asymmetric growth during late-stage evolution, probably triggered by the establishment of a stable system of unidirectional currents and nutrient flux. While colour band counts, related to the AMS ¹⁴C ages, support a seasonal to annual accretion of macroscopic growth bands in the inner concentric and complete outer parts of the skeleton, incremental growth rates at the condensed side are highly variable, as documented by hiatuses and unconformities. Thus the specimen proves that growth rates of bamboo corals may vary within individual skeletons and strongly deviate from the annual mode, hence showing implications on paleoceanographic proxy analyses.     

Microstructure, growth banding and age determination of a primnoid gorgonian skeleton (Octocorallia) from the late Younger Dryas to earliest Holocene of the Bay of Biscay

A fossil primnoid gorgonian skeleton (Octocorallia) was recovered on the eastern Galician Massif in the Bay of Biscay (NE Atlantic) from 720 m water depth. The skeleton shows a growth banding of alternating Mg–calcitic and organic (gorgonin) increments in the inner part, surrounded by a ring of massive fibrous calcite. Three calcite-dominated cycles, bounded by thick organic layers, consist of five light-dark couplets of calcite and gorgonin. Two AMS-¹⁴C datings of the fossil skeleton give ages of 10,880 and 10,820 ± 45 ¹⁴C years before present (BP). We arrive at a calibrated age range of 11,829–10,072 cal. years BP (two σ), which comprises the late Younger Dryas to the earliest part of the Holocene. The cyclic calcitic–organic growth banding may be controlled by a constant rate of calcite secretion with a fluctuating rate of gorgonin production, possibly related to productivity cycles. The skeletal fabric change of alternating calcitic–organic increments to massive fibrous calcite may be the result of hydrographic changes during the deglaciation as reflected by preliminary stable isotope data. If this hypothesis proves to be correct, primnoid gorgonians are able to match with varying hydrodynamic conditions by changing their biomineralisation mode.     

New lucinid bivalves from shallow and deeper water of the Indian and West Pacific Oceans (Mollusca,Bivalvia, Lucinidae)

Four new species and a new genus of lucinid bivalves are described from shallow and deeper waters in the Indian and West Pacific Oceans. The new genus Scabrilucina (subfamily Lucininae) includes the little-known Scabrilucina victorialis (Melvill, 1899) from the Arabian Sea and Scabrilucina vitrea (Deshayes, 1844) from the Andaman Sea as well as a new species Scabrilucina melvilli from the Torres Strait off northeastern Australia. Ferrocina brunei new species (Lucininae) was recovered from 60 m near oil drilling activities off Borneo; its anatomy confirmed the presence of symbiotic bacteria. Two unusual deeper water species of Leucosphaerinae are described, both species included in on-going molecular analyses; Gonimyrtea ferruginea from 400–650 m in the southwest Pacific and Myrtina reflexa from 200–825 m off Zanzibar and Madagascar.     

Distribution of living planktonic foraminifera in the Ross Sea and the Pacific sector of the Southern Ocean (Antarctica)

In order to determine the factors controlling the distribution of planktonic foraminifera as a proxy for reconstruction of paleoenvironments, we present data on live assemblages collected in the Southern Ocean. Plankton tows and hydrographic measurements were taken in the upper 400 m of the water column at different sites in the Ross Sea (site B) and at the Polar Front of the Pacific Ocean (site O) during austral summers from 1998 to 2003.Based on qualitative micropaleontological observations we discriminated between Neogloboquadrina pachyderma dextral (dex) and N. pachyderma sinistral (sin). In addition for N. pachyderma (sin) we distinguished four morphs: the first one (1) has a thickened test and depressed sutures; the second morph (2) is represented by specimens characterized by a subspheric and heavily encrusted test; the third morph (3) has a thin and lobate walled test; the fourth one (4) represent the juvenile stage of N. pachyderma (sin) and is characterized by a smaller average size.The microfauna collected in the Ross Sea (site B) is characterized by the dominance of N. pachyderma (sin) (morphs 1 and 2), whereas low occurrences of Turborotalia quinqueloba, N. pachyderma (dex) and Neogloboquadrina dutertrei were noted in the first 50 m of the water column. The water column at this station is characterized by a marked and shallow stratification and a marked thermocline during the sampling season.At the ocean station (site O), the assemblage shows increasing diversification: T. quinqueloba, G. bulloides, N. pachyderma (dex) and few specimens of Globigerinita uvula characterize the planktonic microfauna. There is a predominance of non-encrusted morphs and juvenile specimens (3 and 4). At this station the mixed surface layer is deeper than in the Ross Sea (60–70 m), the pycnocline and the thermocline less marked.The depth and the intensity of the Deep Chlorophyll Maximum (DCM) influence foraminiferal distribution: N. pachyderma (sin) shows abundance peaks at or just below the DCM while G. bulloides peaks above the DCM. Coiling direction of N. pachyderma seems to be not controlled exclusively by Sea Surface Temperature (SST): probably the two coiling types are genetically different.Results document that diversity of planktonic foraminifera, number of specimens and variations in test morphology are related to regional differences in water properties (temperature, salinity, and DCM depth).     

Degradation of the upper pulvinus in modern and fossil leaves of Cercis (Fabaceae)

Identification of fossil leaf impressions as Cercis has been questioned based upon the presence or absence of a pulvinus at the base of the lamina (upper pulvinus). In the present study, leaves of Cercis canadensis were examined before and after abscission to explore the degradation processes that could occur prior to fossilization, and the North American record for fossil foliage of Cercis was revised accordingly. Results for C. canadensis indicate that: (1) the pulvinus consists largely of tissues with nonlignified cells (a wide cortex, a nonlignified fiber sheath, phloem, and pith) that degrade rapidly after leaf abscission, (2) the lignified xylem tissue that remains in the pulvinus after degradation is in brittle strands, (3) the pulvinus degrades at a faster rate than the lamina or the petiole, and (4) the degraded pulvinus cushion leaves a semicircular pattern on the lamina. From examination of fossils as well as extant species, we: (1) demonstrated that in fossils, the upper pulvinus can show a greater degree of degradation than the adjoining petiole or lamina tissue, suggesting the degradation of upper pulvinus tissue is similar in modern vs. fossil specimens, (2) defined numerous other laminar characters that can be used in conjunction with, or in the absence of, an upper pulvinus to confirm the presence of Cercis in the fossil record, and (3) showed from those criteria that the earliest known North American fossil leaf record for Cercis, from a specimen newly reported in the present study, is from the middle Miocene Succor Creek flora of Oregon.     

Loss of planktotrophy and speciation: geographical fragmentation in the deep-water gastropod genus Bathytoma (Gastropoda,Conoidea) in the western Pacific

Dispersal capabilities are crucial in how speciation patterns are determined in marine invertebrates. Species possessing a long-living planktonic larva apparently have a dispersal advantage over those with non-planktotrophic development, and their distant populations may exchange genetic material, maintaining a broad geographical range for the species. Recent species of the gastropod genus Bathytoma (Conoidea) are all characterized by non-planktotrophic development, having most probably lost a free-swimming larva in the pre-Pliocene, as Miocene fossils have protoconchs indicating planktotrophic larval development. All have a bathyal distribution (100–1500 m), which implies that their capability for direct expansion on the bottom is restricted by both deep-sea basins and shallow-water areas, especially in insular West and South-West Indo-Pacific. Therefore, it can be hypothesized that Bathytoma populations should represent numerous, mostly allopatric taxa restricted to a single or contiguous island groups. We tested this hypothesis using molecular and morphological characters independently. One hundred and thirty-eight specimens from the Philippines, Solomons, Vanuatu, and the Coral Sea were sequenced for one mitochondrial (COI) and one nuclear (ITS2) gene, and 14 operational molecular units were recognized. When these molecular units are overlaid over shell characters, 13 species (11 unnamed) and one form of uncertain status are recognized: three occur in the Philippines, six in the Solomons and one in New Caledonia. Broad distributions (inter-archipelagic) are uncommon (three species). On the whole, the phylogeographic pattern of the diversity in the genus is rather complex and probably also reflects processes of sympatric and fine-scale allopatric speciation, and local extinctions. The eleven new species are described and named.     

Sea surface distribution of coccolithophores in the eastern Pacific sector of the Southern Ocean (Bellingshausen and Amundsen Seas) during the late austral summer of 2001

Horizontal distributions of coccolithophores were observed in sea surface water samples collected on the RV Polarstern between 27 February and 10 April, 2001, in the Pacific sector of the Southern Ocean (Bellingshausen and Amundsen Seas). These samples were analyzed to gain information about the distribution of coccolithophores in relation to the oceanic fronts of the Southern Ocean. A total of fifteen species of coccolithophores were identified, showing cell abundances of up to 67 × 10³ cells/l down to 63°S. Emiliania huxleyi was the most abundant taxon, always accounting for more than 85% of the assemblage. The second most abundant species was Calcidiscus leptoporus, with values lower than 7%. Cell density increases significantly in both the Subantarctic and Polar Fronts (155 and 151 × 10³ cells/l, respectively), decreasing abruptly in the intervening Polar Frontal Zone and to the south of the Polar Front. Although temperature at high latitudes is the main factor controlling the biogeographical distribution of coccolithophores, at the regional level (Southern Ocean) the frontal systems, and consequently nutrient distribution, play a crucial role.     

Temperature- and size-dependent growth and movement of the North Pacific giant octopus (Enteroctopus dofleini) in the Bering Sea

Octopus growth and movement occurs during all life stages and have implications for survival, food web dynamics and reproduction. From 2009 to 2011, 1714 North Pacific giant octopus (Enteroctopus dofleini) were tagged and recaptured in the eastern Bering Sea with visible implant elastomers to better understand the ecology of this data-poor species. Over this period, 246 of the tagged individuals were recaptured. In autumn, when temperatures were warmest, E. dofleini had higher growth rates and moved more than in the colder winter months. For both short- and long-term recaptures, small octopus grew faster than large octopus. Movement of octopus over short- and long-term periods was low for very small and very large octopus and high for median-sized octopus, which is likely to be a function of maturity status and reproductive activities. Approximately 80% of recaptures moved less than 2?km from the initial tagging location for time periods up to a year, suggesting long-term site fidelity. As temperature and size may be tightly linked to growth and movement rates for E. dofleini in the eastern Bering Sea, predicted climate warming will likely alter ecological processes for the species and impact their distribution.     

Histology and growth pattern of the pachy-osteosclerotic premaxillae of the fossil beaked whale Aporotus recurvirostris (Mammalia, Cetacea, Odontoceti)

Beaked whales (Ziphiidae) often show highly specialized features, involving bone morphology or structure, in the rostral region of their skulls. Previous studies revealed an extremely derived and peculiar histological structure in the rostrum of the extant Mesoplodon densirostris. In order to assess if this structure is a general feature of ziphiids, the swollen premaxillae of Aporotus recurvirostris, a Miocene species from the North Sea, were studied histologically. These bones are pachyostotic and strongly osteosclerotic. However, their structural organization is entirely different from that of M. densirostris rostrum: they are basically made of a non-remodeled, laminar tissue that was cyclically deposited by the periosteum. As compared to the generalized structure of the premaxillae of toothed whales exemplified by the bottlenose dolphin, Tursiops truncatus, the pachyostotic condition of Aporotus premaxillae was obviously due to a particularly high and sustained growth-rate, occurring in a dorso-lateral direction. The osteosclerotic structure of these bones resulted from a complete lack of inner resorption activity. The histological features of Aporotus premaxillae indicate that these bones are not likely to have been hypermineralized, and thus, their physical properties must have differed from those of the M. densirostris rostrum. The possible functional involvements of rostral peculiarities in beaked whales are discussed with reference to the whole set of available comparative data.     

Dental anomaly in a fossil squalodont dolphin from New Zealand,and the evolution of polydonty in whales

Abstract

A fragment of mandible of an indeterminate squalodontid dolphin (Upper Oligocene or lowermost Miocene, New Zealand) has 2 anomalous single-rooted teeth intercalated between typically squalodontid anterior cheek-teeth. The anomalous teeth are considered to be truly supernumerary, and not homologous with any erupted teeth in phylogenetically earlier Cetacea. This type of anomaly appears not to have been reported previously for any fossil cetacean. Polydonty, a characteristic of extant odontocetes, was probably attained initially in primitive odontocetes by intercalation of permanent and deciduous teeth, and later was elaborated by the addition of supernumerary teeth. The present specimen represents a morphological (but not phylogenetic) stage between odontocetes with limited and advanced polydonty. Some fossil mysticetes and embryonic extant mysticetes are also polydont, but mysticete polydonty and that of odontocetes have probably evolved convergently.     

Carbon and nitrogen relationships in the feeding and growth of the Pacific oyster, Crassostrea gigas (Thunberg)

Bivalve molluscs, in common with consumers in general, use behavioral and physiological mechanisms to balance metabolic requirements with available nutrients. This study considered how the Pacific oyster, Crassostrea gigas, meets the demands of growth and maintenance, measured in terms of carbon and nitrogen, in a variable food environment. Stoichiometry theory helped to evaluate: a) whether feeding behaviour modifies the intake of C and N given seasonal variability in food quality: b) how rates of metabolism and excretion, and C and N growth efficiencies, respond to mismatch between nutrient intake and the oysters' needs. Two field experiments in the Port Stephens estuary, near Sydney, Australia, measured feeding behaviour, metabolic and growth rates relative to seasonal changes in food supply. In a laboratory experiment, relationships between physiological rates and growth were measured to test a model of growth as a function of absorption of C and N. Potential metabolic targets for compensation were the C/N ratios of body tissues, maintenance and/or of soft tissue added as growth. C/N of whole soft issues varied little during the year (mean 5.4). In July (a time of low food availability of poor quality) growth was negligible and the C/N (maintenance) target was 6.7. In March (abundant food of high quality) growth was rapid with a high N-demand; the C/N of growth was 3.9. In November (medium food quality) there was an enhanced C-demand for glycogen storage; the C/N of growth was 7.9. Feeding behaviour changed the balance between C and N intake across months, primarily due to changes in the selection efficiency for nitrogen, which was highest at low filtration rates on particles of high C/N ratio. Nitrogen intake was favoured over C in July. In November, C-intake increased relative to N. In March, when abundant food nitrogen coincided with a high demand for growth, feeding behaviour was neutral with respect to C/N ratios. In all cases C/N of absorbed matter was greater than the C/N of growth. Growth efficiencies for carbon declined with increased C/N of ingested matter due to higher metabolic increments (SDA) when feeding on lower food quality; the metabolic costs of growth did not vary. In contrast, growth efficiencies for nitrogen did not alter with C/N for ingested matter, due in part to increased nitrogen losses, relative to tissue nitrogen content, when feeding on low C/N food. Nitrogen was therefore conserved metabolically relative to C. Both feeding and metabolic processes contributed to compensation for the mismatch between seasonally variable food quality and the demands of growth.     

The evolution and impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Asia and the Pacific region

The Asia and the Pacific region was within the IAEA program on radiation and tissue banking, the most active region. Most of the tissue banks in the Asia and the Pacific region were developed during the late 1980s and 1990s. The initial number of tissue banks established or supported by the IAEA program in the framework of the RCA Agreement for Asia and the Pacific region was 18. At the end of 2006, the number of tissue banks participating, in one way or another in the IAEA program was 59. Since the beginning of the implementation of the IAEA program in Asia and the Pacific region 63,537 amnion and 44,282 bone allografts were produced and 57,683 amnion and 36,388 bone allografts were used. The main impact of the IAEA program in the region was the following: the establishment or consolidation of at least 59 tissue banks in 15 countries in the region (the IAEA supported directly 16 of these banks); the improvement on the quality and safety of tissues procured and produced in the region reaching international standards; the implementation of eight national projects, two regional projects and two interregional projects; the elaboration of International Standards, a Code of Practice and a Public Awareness Strategies and, the application of quality control and quality assurances programs in all participating tissue banks.     

Zonation, behaviour and morphology of the intertida coral-treader Hermatobates (Hemiptera: Hermatobatidae) in the south-exst Pacific

The coral-treaders (Hermatobatidae) are the only exclusively marine family of insects. Observations in the Cook Islands, Samoa, Tonga and Fiji show that the insects can be abundant on shores that provide rocks with cavities that remain air-filled during high tide. The zone of suitable habitats for the insects is restricted to a narrow ( c. 20 cm) vertical band roughly centred around Mean Low Water Neaps. Transplant experiments show that the insects are unable to survive above or below this zone. The insects emerge from their rocky crevices about an hour before low tide, swim on the water surface during low tide, and return to their crevices about an hour after the tide has turned. There are only four larval instars, which can be readily separated by their morphology. Electron microscope studies show that the insects are clothed in a layer of micro-hairs of unique design: a short tapering shaft tipped with a sphere. These micro-hairs may act as a plastron: their distribution corresponds precisely to the pattern of the silvery 'air-layer' seen when the insects are submerged, their spherical tips provide a regular array that could support an air-water interface, they occur at high densities (up to 3.5 times 10⁶ mm^-2), and the layer makes connection with the thoracic spiracles. Half the insects were able to survive submergence in recirculated seawater for 12 hours. The adults appear to swim further from shore than the larvae, and they were observed copulating in tidal pools.     

Scale morphogenesis and ultrastructure of dermis during embryonic development in the alligator (Alligator mississippiensis, Crocodilia, Reptilia)

Formation of scales in different body regions of embryonic alligators is described using light and electron microscopy. Transformation of the skin surface to produce scales takes place between stages 19 and 23, after which the shape of scales is complete over most of the embryonic surface. Scalation is not synchronous; different regions develop scales at different rates. Initially scales are formed on the back and dorsal side of the proximal tail and appear as undulations of the epidermis which form symmetrical (bumps) or asymmetrical (serrated) scale anlagen. No dermal condensations are apparent beneath the epidermis, although in some areas of the skin (belly, limbs) mesenchymal cells are more numerous within the bumps than in other areas. At stage 21, scalation has spread to the neck and belly but is absent or poorly developed over most areas of the flank, gular, jaw, limb and head regions. Grooves form between the outer edges of adjacent scales or interbump regions. A superficial denser dermis and a reticulated deep subdermis are visible in many scales from stage 21. The dermis forms a superficial loose and a deep dense layer from stage 22. Both loose and deep dermis, and sometimes the deep reticulate subdermis, move towards the surface to form the dermal core of scales, although the mechanism of this movement is not known. Bundles of collagen fibrils, with almost no elastic fibrils, are progressively deposited, especially in the denser dermis. At stage 22, the flank, gular and proximal areas of limbs form scales, but the head, jaw, distal limbs and digits still lack scales. The digits become scaled at stage 23 when scalation is well advanced in the other regions. By stage 24 most of the body is scaled and subsequent scale modifications occur only by growth. Five main types of scales are recognized by their shape: symmetrical scutes, asymmetrical scutes, overlapping scutes, tuberculate scales, and elevated asymmetrical scutes (tail verticils). Pigmentation, mainly due to epidermal melanocytes, is visible at embryonic stage 23 and progresses through stages 24 and 25.     

Diversity, biomass and distribution pattern of Sargassum beds in the South West lagoon of New Caledonia (South Pacific)

Sargassum (Phaeophyceae, Fucales) is a genus of worldwide distribution recently recognised to proliferate in several regions of the South Pacific. In New Caledonia, species of this genus naturally structure one of the major lagoon habitats but their extent, composition and biomass remain largely unknown. To fill these gaps in our knowledge over large areas, we applied a combination of remote sensing and in situ methods applied to the Neo Caledonian South West Lagoon. Space borne high resolution Landsat (30-m resolution) and Quickbird (2.4-m resolution) images of the Neo Caledonian South West lagoon were used to estimate the spatial extent of the different beds of interest. Species composition was determined for 11 Sargassum beds and seasonal variations were investigated for four representative beds over an 18 month period using quadrats and transects. Relationships between surface cover and biomass were estimated from seasonal field data sets. Finally, four methods requiring variable levels of sampling effort were designed to estimate the total biomass at the scale of each bed, considering (or not) the specific composition, and spatial and temporal variations. Seven Sargassaceae species were identified. Mean surface cover (24.4–51.6%) and total biomass [3.4–1,461.9 t dry matter (DM)] varied widely between beds. Overall, biomass temporal variations were not significantly different, but species-level variations seemed to be bed-specific. The extent of the 11 beds was 9 km²; their total biomass was estimated and compared using each of the four methods, and the most precise method provided an estimate of 2,900 t DM. This study demonstrates a way of characterising Sargassum beds, efficiently and on a large scale, using a combination of remotely sensed and in situ data. These methods should be useful for possible future biomonitoring of Sargassum beds in New Caledonia, and in other areas worldwide.     

Dietary administration of zingerone to enhance growth, non-specific immune response, and resistance to Vibrio alginolyticus in Pacific white shrimp (Litopenaeus vannamei) juveniles

Zingerone, one of the active components of ginger, is a phenolic alkanone with antioxidant and anti-inflammatory properties. The effects of zingerone supplementation on the growth, immunity, and disease resistance of Pacific white shrimp (Litopenaeus vannamei) juveniles were studied. Four experimental diets, including a control diet (without zingerone enrichment) and 1, 2.5, and 5 mg zingerone (kg diet)⁻¹ were used. After 56 days of culture, shrimp fed diets supplemented with 1, 2.5, and 5 mg zingerone (kg diet)⁻¹ had significantly greater weight gain and feed efficiency than the controls. Furthermore, after 56 days of culture, shrimp fed all doses of the zingerone diet had higher survival rates compared to the controls after 24-72 h of challenge by the pathogen, Vibrio alginolyticus. Significantly increased phenoloxidase levels were found in shrimp fed the zingerone diets at all doses, and respiratory bursts, lysozyme and phagocytic activities of shrimp fed 2.5 and 5 mg zingerone (kg diet)⁻¹ also significantly increased. Neither the total hemocyte count nor superoxide dismutase activity of the experimental and control groups revealed significant differences at any dose. The results indicate that zingerone can be recommended as a supplement to shrimp feed to increase growth, immunity, and disease resistance against the pathogen, V. alginolyticus. Use of zingerone as appetizer and immunostimulant in shrimp is promising.     

High survival and growth rates of introduced Pacific oysters may cause restrictions on habitat use by native mussels in the Wadden Sea

Pacific oysters Crassostrea gigas (Thunberg, 1793) were introduced to the northern Wadden Sea (North Sea, Germany) by aquaculture in 1986 and finally became established. Even though at first recruitment success was rare, three consecutive warm summers led to a massive increase in oyster abundances and to the overgrowth of native mussel beds (Mytilus edulis L.). These mussels constitute biogenic reefs on the sand and mud flats in this area. Survival and growth of the invading C. gigas were investigated and compared with the native mussels in order to predict the further development of the oyster population and the scope for coexistence of both species. Field experiments revealed high survival of juvenile C. gigas (approximately 70%) during the first three months after settlement. Survival during the first winter varied between > 90% during a mild and 25% during a cold winter and was independent of substrate (i.e., mussels or oysters) and tide level. Within their first year C. gigas reached a mean length of 35-53 mm, and within two years they grew to 68-82 mm, which is about twice the size native mussels would attain during that time. Growth of juvenile oysters was not affected by substrate (i.e., sand, mussels, and other oysters), barnacle epibionts and tide level, but was facilitated by fucoid algae. By contrast, growth of juvenile mussels was significantly higher on sand flats than on mussel or oyster beds and higher in the subtidal compared to intertidal locations. Cover with fucoid algae increased mussel growth but decreased their condition expressed as dry flesh weight versus shell weight. High survival and growth rates may compensate for years with low recruitment, and may therefore allow a fast population increase. This may lead to restrictions on habitat use by native mussels in the Wadden Sea.