Comparing bird assemblages in large and small fragments of the Atlantic Forest hotspots

The Atlantic Forest (AF) is one of the five most threatened and megadiverse world hotspots. It is arguably the most devastated and highly threatened ecosystem on the planet. The vast scope of habitat loss and extreme fragmentation in the AF hotspots has left intact very few extensive and continuous forested fragments. We compared bird assemblages between small (<100 ha) and large (>6,000 ha) forest remnants, in one of the largest AF remnants in Argentina. We performed 84 point-counts of birds in four large fragments (LF) and 67 points in 25 small fragments (SF). We recorded 4,527 bird individuals belonging to 173 species; 2,632 belonging to 153 species in LF and 1,897 in 124 species in SF. Small fragments suffered a significant loss of bird richness, mainly forest dependent species, but the birds abundance did not decrease, due to an increase in abundance of forest independent and semi-dependent bird species (edge and non forest species) that benefit from forest fragmentation. The bird guilds of frugivores, undestory, terrestrial and midstory insectivores, nectarivores and raptors, and the endemic species of AF were area sensitive, decreasing significantly in richness and abundance in the SF. Terrestrial granivores were the only guild positively affected by forest fragmentation, containing mainly edge species, which forage in open areas or borders including crops. Our first observations on fragmentation effects on bird assemblages in the southernmost Argentinean Atlantic Forests did not validate the hypothesis on pre-adaptation to human disturbances in the bird communities of AF. On the contrary, we observed that forest dependent, endemic and several sensitive bird guilds were strongly affected by fragmentation, putting in evidence the vulnerability to the fragmentation process and the necessity to conserve large remnants to avoid reduction of the high biodiversity of AF birds.     

Deep-sea asellote isopods of the north-east Atlantic: the family Thambematidae

A collection of thambematids (Crustacea, Isopoda, Asellota) from depths of 1400–2900 m in the Rockall Trough, west of the British Isles, is considered. The type species of the genus Thambema Stebbing, T. amicorum Stebbing, is rediagnosed and three new species, T. golanachum, T. tanum , and T. fiatum , are described. The genera Thambema and Microthambema Birstein are contrasted and taxonomic characters separating these genera are provided. The difficulty of providing effective definitions for higher category taxa is discussed and a new definition is provided for the Asellota.     

Grazing impact of copepod assemblages and gravitational flux in coastal and oceanic waters off central Chile during two contrasting seasons

In evaluating carbon flux in coastal and oceanic waters offcentral Chile (~36°S), the grazing pressure by copepod size-assemblagesand the gravitational flux from the surface layer were estimatedduring two contrasting seasons: spring upwelling (October 1998)and winter (July 1999) periods. Grazing pressure upon phytoplanktonbiomass was small (<5%) during both periods at all stations.It was, however, an important proportion of primary productionat the coast during the spring (17–43%) but minimal inwinter (<5%) while, at the oceanic station, it was significantduring both seasons (13–46%). Similarly, the downwardflux of particulate organic carbon was a significant percentageof primary production at the coast during the spring (31%) andless so in winter (15%); at the oceanic station, it was a higherfraction during both seasons (46–47%). Copepod pelletswere only a minor component of the faecal flux, suggesting thatthey were rapidly recycled in the water column. The seasonaldifferences in these carbon fluxes in the coastal upwellingzone were related directly to the larger quantities of organicmatter in the water column during the spring upwelling period,including higher chlorophyll a concentrations and primary productionrates. During the winter, the particulate organic carbon appearsto be mainly recycled in the water column. In the oceanic zone,in contrast to what is expected, a large percentage of the primaryproduction appears to be exported during both periods, thoughconsumption by copepod assemblages was also important, suggestingsignificant horizontal carbon export from the coast to the openocean.     

Modern whaling in Britain and the north-east Atlantic Ocean

Modern whaling, using an explosive harpoon fired from a steam catcher-boat to kill the fast-swimming rorquals, began from shore whaling stations in northern Norway in the 1860s. It spread to Iceland, the Faeroe Islands and Spitsbergen, before reaching the British Isles in 1903.
Whaling took place from four stations in the Shetland Islands, one in the Outer Hebrides, and two in Ireland, before the First World War. Fin whales were the main species caught but Blue, Humpback, Sei, Right, Sperm and Bottle-nosed whales were also taken. Four stations re-opened in 1920, but from 1923 onwards only two continued to operate and whaling ceased in 1929, though the Hebridean station worked again for two seasons in 1950–1951.
The species composition of catches at the Hebridean and Irish stations was very similar and different from that of the stations in the Shetland Islands where few Blue whales and Right whales were taken. There is evidence that Fin whales were being overfished on the Shetland Islands whaling grounds at an early date, and that Blue whales and Right whales, but not Fin whales, declined in numbers on the Hebridean grounds.
The history of modern whaling in the north-east North Atlantic region as a whole indicates that the stocks of Blue, Humpback and Right whales were not large enough to support continuous whaling on the scale which took place there. The development of whaling since 1945 supports the view that there are separate populations of Fin whales in the region. The numbers of this species have declined on the whaling grounds of the Faeroe Islands and western Norway, and possibly also of north Norway, but not on the Icelandic grounds where there is no evidence of overfishing.     

Atlantis II Cruise: uniformity of deep copepod assemblages in the Mediterranean Sea

Studies of the community structure and biomass of deep copepodsbelow 500 m from R/V Atlantis II cruises AII49 and AII59 inMay–June 1969 and September–October 1970 denoteuniformity in deep assemblages among all major Mediterraneansubregions. Of the 65 copepod species recorded from 600–2500m, 45 were common for both Western and Eastern basins Eightof these species were dominant for all deep Mediterranean waters,comprising 77% of the deep plankton population The uniformityof deep copepod assemblages was confirmed by the Mantel testapplied to a simulated sampling procedure Only in terms of biomassdid Western and Eastern basins show appreciable regional differenceswith highest values for density and volume characterizing Westernstations ¹Died tragically at sea during the course of a cruise on December15, 1988     

Some deep water Pycnogonids from the north-east Atlantic

Twenty-two specimens of pycnogonid representing nine species arc recorded from deep waters around the British Isles. The samples are from the Faroe Channel, the Hebridean Terrace and the vicinity of the Great Sole Bank, taken at depths of between 200 and 1835 m. These specimens demonstrate marked southern range extensions for Aymphon teptocheles and Pallenopsis tritonis , and include the northernmost record for the genus Cilunculus ( C. alcicornis ) and the third European record for Colossendeis arcuata . Protonymphon larvae of N. leptocheles and Paranymphon spinosum are figured.     

Basin-scale latitudinal patterns of copepod grazing in the Atlantic Ocean

Size-fractionated copepod abundance and ingestion rates wereinvestigated along a 50°S–50°Nlatitudinal transect,during the Atlantic Meridional Transect (AMT) 4, 5 and 6 cruises(boreal spring–autumn 1997, boreal spring–summer1998). Copepod abundance was higher at high latitudes in spring,near northwest Africa, in the equatorial and Benguela upwellingsystems, and in the Subtropical Convergence, and lower in oligotrophicgyres. Gut contents were not related to phytoplankton biomassor production. Gut evacuation rate averaged 0.03 min^-1, andwas not related to latitude or body size. Conservative estimatesof copepod community total ingestion rates ranged between 3.4and 173 mg C m^-2 day^-1 for AMT4, 1.6–252 mg C m^-2 day^-1in AMT5 and 10–160 mg C m^-2 day^-1 in AMT6. Maximum valueswere always in the upwelling regions, the subtropical convergenceand high latitudes in the Northern Hemisphere during borealspring. Calculated ingestion rates translate into average dailyminimal consumption values of 2.07%, 1.89% and 2.6% of totalchlorophyll stock, or 8.02%, 14.5% and 12.9% of total primaryproduction ingested daily on AMT4, 5 and 6 respectively. Grazingimpact increases considerably if we consider ingestion of phytoplanktonlarger than 2 µm, especially under the influence of theEquatorial and North African upwellings, where copepod ingestionrepresents up to 30% of the biomass and >100% of productionby large cells.     

Body size regulation in copepod crustaceans

Body size affects survival probabilities, reproductive output and individual fitness in many organisms. In freshwater zooplankton, traits ranging from demographic rates to community composition depend on body size, and predation is most often identified as the selection pressure determining body size. We examined the extent to which stage-specific growth trajectories and body sizes of copepod crustaceans are constrained, independent of selection. We used exuviae shed at each molt to quantify the relationship between size at molting and growth during the subsequent instar for two common, herbivorous calanoid copepods, Boeckella triarticulata and Diaptomus leptopus. Individuals of both species were raised under diets of different food quality or quantity, and at different temperatures. Size at molting varied little among individuals of both species, as a consequence of a persistent negative relationship between size at molting and subsequent (absolute) growth increment. Individuals that were small when they molted grew more during the subsequent instar than individuals that were large. This relationship was statistically significant for nearly all instars of both species raised in different food or temperature conditions, and not affected by food quality, food quantity or temperature. Our results indicate that body size is constrained or regulated over much of the copepod life cycle, independent of the effects of environmental conditions (food, temperature, predation). Received: 26 December 1998 / Accepted: 13 September 1999     

Disturbance and organization of macroalgal assemblages in the Northwest Atlantic

Australian Institute of Marine Science Contribution no. 436.     

Zonal distribution and seasonal vertical migration of copepod assemblages in the Scotia Sea

Large, biomass-dominant Southern Ocean copepod species have been much studied, but small and mesopelagic species also play major rôles in these ecosystems. However, little is known of some basic aspects of their ecology. To address this, the abundances of 23 copepod species and genera were analysed from 72 stations sampled during the Discovery Expeditions in the 1920s to 1950s. Stratified net samples, usually to a depth of 1000?m, provided year-round coverage in the Scotia Sea from the Subantarctic Front to the Weddell-Scotia Confluence. Small copepods (Microcalanus pygmaeus, Ctenocalanus spp., Oncaea spp. and Oithona spp.) formed ～75% of total copepod abundance in the top 1000?m across all major zones. Oithona spp. composed ～40% of copepod numbers in the Polar Front area and to its south: further north their importance declined. All mesopelagic taxa except for the warmer-water species Metridia lucens and Pleuromamma robusta, extended throughout the entire study area, with smaller regional differences than for the shallower-living species. The species showed a continuum of temperature ranges, and there was no evidence that the Polar Front was a major biogeographic boundary to their distribution. Indeed, several important species, including Oithona spp. (mainly Oithona similis), Ctenocalanus spp., Metridia lucens and Rhincalanus gigas reached maximum numbers in this area. Total copepod abundance was thus higher in the vicinity of the Polar Front than in any other region. Only two copepod families made pronounced seasonal vertical migrations: Eucalaniidae (Eucalanus longiceps and R. gigas) and Calaniidae (Neocalanus tonsus, Calanoides acutus, Calanus simillimus and Calanus propinquus). Some evidence for a winter descent was found for Ctenocalanus spp. and some deeper-living groups: Euchaeta spp. and the Metridiidae, although their migrations were not so great as for the eucalanids and calanids.     

Disturbance and organization of macroalgal assemblages in the Northwest Atlantic

Large seaweeds are often structurally dominant in subtidal and intertidal rocky shore benthic communities of the N.W. Atlantic. The mechanisms by which these algal assemblages are maintained are surprisingly different in the two habitats. In the subtidal community, kelps are dominant space competitors in the absence of strong grazing interactions. In contrast, the large perennial seaweeds of intertidal zones (fucoids and Chondrus crispus) are competitively inferior to both sessile filter feeders and ephemeral, pioneer algal species. Intertidal seaweed beds are maintained by carnivory of whelks, which reduces filter feeder populations, and by herbivorous periwinkles which reduce ephemeral algal populations. Through most of the intertidal zone, disturbance, both biological and physical, dictates which species shall compete and equilibrium conditions obtain subsequently.The roles of subtidal consumers are quite different. Sea urchins are the major algal herbivores and these voracious animals maintain an equilibrium state in which large tracts of subtidal coralline pavement are kept free of kelp forests. Urchins do not seem to play a successional facilitative role for kelps in the way that periwinkles do for fucoids in the intertidal. Control of herbivore populations is thus a key to the maintenance of subtidal foliose algal beds. It is clear that parasitic amoebas can decimate sea urchin populations so that kelp forest dominance is assured. However, the importance of carnivory in limiting urchins in the subtidal community is unclear in the absence of appropriate manipulation experiments. It is possible that carnivorous decapods and fin fish control sea urchin populations and hence foliose algal abundance, but this must remain speculative. The seaweed-dominated state of the subtidal system is an alternative equilibrium condition to the urchin/coralline alga configuration. The structure of the kelp beds is relatively uniform in responding to frequent small-scale, infrequent large-scale, or no, disturbance.     

Genetic variation at isozyme loci in blue whiting from the north-east Atlantic

Genetic variation in blue whiting Micromesistius poutassou was investigated by starch gel electrophoresis of enzymes in tissue extracts. A total of 130 specimens from the spawning areas west of the British Isles were collected from trawl catches in 1990 ( n = 30) and 1992 ( n = 100). In 25 tissue enzyme loci screened for genetic variants in the 1990 sample, polymorphisms (0.95 criterion) were found at IDDH-2 *, IDHP-2 * and PGM-1 *, giving a frequency of polymorphic loci of P _0.95= 0.12. In pooled samples the average heterozygosity per locus was estimated at H _e =0.043 and the effective number of alleles per locus at 2.20, 1.45 and 1.53, respectively, for IDDH-2 *, IDHP-2 * and PGM-1 *.     

Spatial distributions of copepod genera along the Atlantic Meridional Transect

The distribution of copepod taxa at a basin scale was analysed using three Atlantic transects (U.K. – Malvinas 1997, Malvinas – U.K. 1997, and South Africa – U.K. 1998). Integrated 200 m to surface zooplankton samples were taken daily, using WP2 nets (200-m mesh). The zooplankton were size-fractionated and sub-samples taken for carbon analysis. The remainder of the samples was preserved for taxonomic analysis of copepod genera. Multidimensional scaling (MDS) was used to identify zoogeographic regions from the copepod genera. Seven regions were identified: northern temperate, northern subtropical, equatorial, southern tropical, southern sub-tropical, southern temperate and Benguela upwelling. Analysis of similarity showed that most regions were significantly different from each other except: northern temperate and southern temperate, northern temperate and southern subtropical, and northern subtropical and southern subtropical. The genera significant in determining the regions were identified. These regions were compared to other schemes of biological and hydrographic areas. The MDS also showed that the copepod composition in the tropical and subtropical regions was less variable than the temperate and Benguela stations. Latitudinal trends in diversity and size were also investigated. Copepod genera showed a reduction in richness at higher latitudes. Copepod size did not show any substantial or consistent change with latitude along these transects, as demonstrated by both the numerical abundances in each size category, and the carbon biomass per individual. The proportion in each size fraction was quite uniform over the transect.     

Seasonality of the copepod assemblages associated with interplay waters off northeastern Taiwan

This study investigated copepod assemblages in the regime around Turtle Island off northern Taiwan to trace South China Sea water (SCSW) flowing northward with the Kuroshio Current. Seasonal variations of copepod assemblages demonstrated a dynamic succession of changes in copepod populations; the average abundance for total copepods ranged from 102.58 ± 53.38 in December to 1669.89 ± 1866.17 in March (individuals m^?3). A total of 87 copepod species representing 36 genera and 21 families were identified. Among all samples, Temora turbinata dominated the copepods by a relative abundance (RA) of 26.89 %, followed by Paracalanus parvus (RA: 22.34 %) and Corycaeus (Ditrichocorycaeus) affinis (RA: 12.77 %). Only the Acrocalanus gracilis species was recorded in all samples. Results of one-way ANOVA revealed that the number of copepod species, indices of richness, evenness, and Shannon–Wiener diversity differed significantly in five different cruises. The density of five copepod species (Gaetanus minor, Calanus sinicus, Eucalanus elongates, Rhincalanus nasutus, and Rhincalanus rostrifrons) exhibited a significant negative correlation with seawater temperature. In contrast, the density of Canthocalanus pauper and Undinula vulgaris was significantly positively correlated with seawater temperature. The cold-water indicator species, C. sinicus, recorded in samples of March and May indicated the effect of China Coast Water (CCW) on copepod communities in the study area. Furthermore, the presence of Calanoides philippinensis in May samples strongly indicated that the SCSW may reach the Turtle Island area. Consequently, C. philippinensis and C. sinicus can be used to trace SCSW and CCW, respectively, in the study area.     

The size distribution of phytoplankton and participate organic matter in the Equatorial Atlantic Ocean: importance of ultraseston and consequences

The size fractionation of paniculate matter (<200, <35,<3 and <1 µm) has been measured in the EquatorialAtlantic Ocean at different stations. Chlorophyll a, phaeophytin,particulate carbon, nitrogen and phosphorus have been analysed.Primary production by ¹⁴CO₂ uptake was also measured with prescreeningtechnique. It appears from this study, that the pariculate matter has avery small size: 40–60% of the chlorophyll passed through1 µm Nucleopore filter, and 75–90% of the paniculatecarbon and nitrogen passed through 3 µm Nucleopore filterin offshore waters. From the atomic ratio C/N, C/P and C/chla, and primary productionvalues, the <3 µm fraction would be mainly constitutedby inactive photosynthetic organisms or partides of detritus.The 3–35 µm fraction, in contrast, would be principallyactive phytoplankton.     

A multivariate analysis of phytoplankton assemblages in the western North Atlantic

Principal component analysis (PCA) of a large data set of phytoplanktonrecords, 1111 stations collected in an uneven sampling patternover a 9-year period from the US north-eastern shelf watersis discussed. Year-to-year variation was found to be the largestcomponent of variation in the data and was more important thanseasonal variation and all but the grossest of geographic variation.Strong seasonal and geographic patterns were detected when long-termtemporal variation was removed and it was possible to identifygroups of critical species influencing geographic patterns.In this study PCA techniques were most successful when usedon data collected from a small geographic area or data collectedfrom a narrow spectrum of time (e.g., a single year or a singlemonth) or both. Interpretation of patterns is difficult if severalmajor sources of variation are present. The major sources ofvariation in phytoplankton populations were identified as annualchanges, seasonal changes and geographic patterns. Distincttrends were identified in the geographic pattern with the southernestuaries, the Mid-Atlantic Shelf and offshore versus coastalzones identified as having distinctive fauna] assemblages.     

Grazing of the copepod Diaptomus connexus on purple sulphur bacteria in a meromictic salt lake

A meromictic lake ecosystem (Mahoney Lake, BC, Canada) was investigated to elucidate the significance of chemocline bacteria in the total carbon cycle under natural conditions. In this lake, primary production by oxygenic phototrophs was insufficient to support the observed net secondary production of the calanoid copepod Diaptomus connexus and the rotifer Brachionus plicatilis , indicating the presence of additional food sources for consumers. Mahoney Lake harbours the densest population of phototrophic sulphur bacteria ever reported in a natural body of water. This layer is located at the interface between oxic and anoxic water layers and is dominated by the purple sulphur bacterium Amoebobacter purpureus . The transfer rates of A. purpureus carbon to D. connexus determined in stratified mesocosms were very low (0.71 ngC copepod⁻¹ day⁻¹) and accounted for only 0.6% of the observed net biomass increase in the zooplankter. Stable stratification within the mesocosms prevented an upwelling of A. purpureus into the oxic part. However, measurements of carbon fluxes, infrared fluorescence microscopy and stable carbon analysis provided cumulative evidence that, under in situ conditions, the cell carbon of purple sulphur bacteria indeed enters the aerobic food chain via the grazing activity of D. connexus . Based on a two-source isotopic mixing model, A. purpureus represents at least 75–85% of the diet of D . connexus . Autumnal upwelling into oxic water layers and aggregation of A . purpureus cells appear to be the main factors determining the high carbon flux from purple sulphur bacteria to zooplankton under natural conditions, and most probably also play a key role in other aquatic ecosystems. Through this pathway, over 53% of the reduced organic matter of purple sulphur bacteria trapped in anoxic bottom waters is returned to the oxic realm.     

First occurrence and new length record for the bigeye thresher shark in the north-east Atlantic

The first confirmed record for the bigeye thresher shark Alopias superciliosus caught in the far north-east Atlantic is described here. The specimen was the longest and heaviest recorded to date. Above-average summer sea temperatures occurred in the catch area in 1995.     

Mesozooplankton Distribution and Copepod Grazing in the Subtropical Atlantic Near the Azores: Influence of Mesoscale Structures

Mesozooplankton distribution and copepod grazing were investigatedin the Subtropical Atlantic Ocean near the Azores during theAZORES I (August) and II (April–May) cruises. Mesozooplanktonbiomass and abundance remained low throughout the region, butsignificant increases were found related to the presence ofthe Azores Front. The Azores Front also exhibited maximum valuesof copepod community ingestion, reaching 250 mg C m^–2ingested daily. This increase in ingestion was related to increasesin copepod abundance, but not in copepod gut contents. No relationshipwas found between gut contents, or ingestion, and phytoplanktonbiomass or production. Daily cycles were found in copepod gutcontents, being higher during the night, but not in copepodabundance. Multi-dimensional scaling analysis revealed differencesin copepod taxonomic composition between both sides of the front.During spring, daily copepod ingestion represents an averageof 6% of the integrated chlorophyll (Chl) a concentration and22% of the primary production. These percentages increase to15% of Chl and 61% of production if we only consider large (>2µm) phytoplankton. No clear influence of the cycloniceddy LETICIA was found in mesozooplankton biomass or grazing.A significant effect of the Great Meteor Tablemount was foundin copepod abundance and grazing, with higher values locatedwest of the mount.     

Grazing by the calanoid copepod Neocalanus cristatus on the microbial food web in the coastal Gulf of Alaska

Neocalanus cristatus feeding on phytoplankton and microzooplanktonwas measured in the coastal Gulf of Alaska during spring andearly summer of 2001 and 2003. Neocalanus cristatus CV fed primarilyon particles >20 µm. Particles in the 5- to 20-µmsize range were ingested in some experiments under nonbloomconditions but not under bloom conditions. Particles <5 µmwere not ingested but increased during incubations because N.cristatus consumed their microzooplanktonic predators. Neocalanuscristatus are sufficiently abundant in nature to induce sucha cascade effect in situ. Microzooplankton provided >70%of the carbon ingested by N. cristatus under nonbloom conditionsbut only