Phosphorus speciation in Myall Lake sediment, NSW, Australia

The amount of phosphorus and its fractions in the sediment of Lake Myall, NSW, Australia, was assessed using a sequential extraction technique. Five sedimentary phosphorus reservoirs were measured, namely loosely sorbed phosphorus (NH₄Cl–P), iron associated phosphorus (BD–P), calcium bound phosphorus (HCl–P), metal oxide bound phosphorus (NaOH–P) and residual phosphorus (organic and refractory P, Res-P). Samples were taken from the deep and shallow sites of the lake. During the analysis, the average concentrations of each fraction of phosphorus was calculated. The results depicted that the total phosphorus (TP) content and chemically extractable phosphorus in both fine and coarse sediment fractions from the deep sites of the lake were significantly higher than those of the shallow sites, except for HCl–P extracted from the fine sediment fraction. Sediment TP was also strongly and positively correlated to sediment Fe. The phosphorus in the sediment mainly consisted of BD–P and Res-P, while NH₄Cl–P and HCl–P only contributed a minor part. The rank order of the different phosphorus extracts was similar for the two sites, namely Residual-P > BD–P > NaOH–P > HCl–P > NH₄Cl–P.     

Modifying living space: an experimental study of the influences of vegetation on aquatic invertebrate community structure

In temporary freshwater systems, the type of vegetation within a system can influence community structure. Vegetation not only provides physical structure, but can also contribute to changes in abundance and quality of food and in water quality through decomposition. An experiment was undertaken using natural and artificial vegetation in small mesocosms to examine the influence of the physical structure of vegetation on invertebrate community structure in terms of water quality, food abundance, and physical structure. It was predicted that invertebrate community structure would be identical in natural and artificial treatments if the effect of vegetative decomposition was negligible. Furthermore, invertebrate community structure in bare ground treatments would be identical to those with vegetation if the physical structure of vegetation has no significant effect. Five treatments were used: a bare ground control, artificial vegetation (×2), and natural vegetation treatments (grass, eucalypt leaf litter). Water quality, food abundance, and invertebrate abundance were examined after six weeks of inundation. All treatments had high water temperatures (34–40°C), and natural vegetation treatments had slightly higher conductivity (208–316 mS cm⁻¹) and lower turbidity (40–231 NTU) than other treatments (47–156 mS cm⁻¹ and 55–400 NTU, respectively). The physical structure of artificial vegetation did not significantly influence invertebrate community structure compared to the bare ground treatment, whereas treatments with decomposing natural vegetation had relatively low abundances of microcrustaceans (0–96 individuals/mesocosm) and relatively high abundances of chironomids (192–1576 individuals/mesocosm) compared to other treatments (>100 microcrustaceans/mesocosm if present, and <370 chironomids/mesocosm, respectively). This suggests that food availability had greater importance than physical structure in determining community structure in these small aquatic ecosystems. Handling editor: S. M. Thomaz     

The specific inherent optical properties of three sub-tropical and tropical water reservoirs in Queensland, Australia

The underwater light climate, which is a major influence on the ecology of aquatic systems, is affected by the absorption and scattering processes that take place within the water column. Knowledge of the specific inherent optical properties (SIOPs) of water quality parameters and their spatial variation is essential for the modelling of underwater light fields and remote sensing applications. We measured the SIOPs and water quality parameter concentrations of three large inland water impoundments in Queensland, Australia. The measurements ranged from 0.9 to 42.7 μg l⁻¹ for chlorophyll a concentration, 0.9–170.4 mg l⁻¹ for tripton concentration, 0.36–1.59 m⁻¹ for a _CDOM(440) and 0.15–2.5 m for Secchi depth. The SIOP measurements showed that there is sufficient intra-impoundment variation in the specific absorption and specific scattering of phytoplankton and tripton to require a well distributed network of measurement stations to fully characterise the SIOPs of the optical water quality parameters. While significantly different SIOP sets were measured for each of the study sites the measurements were consistent with published values in other inland waters. The multiple measurement stations were allocated into optical domains as a necessary step to parameterise a semi-analytical inversion remote sensing algorithm. This article also addresses the paucity of published global inland water SIOP sets by contributing Australian SIOP sets to allow international and national comparison.     

Macrobenthic fauna of the Franz Josef Land archipelago

Benthic fauna of the deeper waters (50–320 m) of the Franz Josef Land archipelago sampled in August 1992 using standard western techniques is described and compared with earlier Russian studies of the archipelago. Three faunal assemblages are recognised at depth ranges between 50–150, 150–300, and >300 m depth. Their distributions are related to depth and to different water masses derived from a mixture of Barents Sea water entering from the south at intermediate depths (20–150 m), and Atlantic water from the north below 300 m. The recorded faunal diversity and biomass is as high as or higher than that from comparable Arctic and northern boreal areas. Comparisons are also made with a complimentary Russian survey in the same area using different techniques. The Russian work collected larger organisms most effectively, whereas the present work recorded the smaller taxa more efficiently. Russian surveys provide complementary data to western studies, but care must be taken when comparing studies as they reflect biases in sampling gear and scientific emphasis. These data intercalibrations are important as Russian archives contain a wealth of information that, if used correctly in association with western data sources, will be useful in environmental monitoring studies as human activities increase in the Eurasian Arctic. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Growth and survival of the invasive alga, <Emphasis Type="Italic">Caulerpa taxifolia</Emphasis>, in different salinities and temperatures: implications for coastal lake management

The alga Caulerpa taxifolia is an invasive pest species in many parts of the world and has recently become established in several estuaries in south eastern Australia. A major infestation has occurred in Lake Conjola, an intermittently open and closed coastal lagoon in southern NSW. Short term (1 week) laboratory experiments were carried out to investigate growth and survival of fragments of C. taxifolia collected from this outbreak, under a range of salinities (15–30 ppt) and water temperatures (15–30°C). Fronds, stolons and thalli of the alga all displayed similar responses. Many of the algal fragments doubled in size over the week and a maximum growth rate of 174 mm/week was recorded. Fragments showed good growth (> 20 mm/week) at salinities > 20 ppt and temperatures > 20°C. Almost total mortality occurred at salinities lower than 20 ppt and temperatures less than 20°C. Historical records of water quality demonstrate that prior to entrance manipulation in 2001, salinities in Lake Conjola had often dropped to below 17 ppt for extended periods (up to 2 years). This suggests that management of the alga may be improved if the lake was allowed to undergo its normal cycles of opening and closing to the ocean, and that entrance manipulation may be one factor that has influenced the success of this invasive species.     

Statistical analysis of structural characteristics of protein Ca<Superscript>2+</Superscript>-binding sites

To better understand the biological significance of Ca²⁺, we report a comprehensive statistical analysis of calcium-binding proteins from the Protein Data Bank to identify structural parameters associated with EF-hand and non-EF-hand Ca²⁺-binding sites. Comparatively, non-EF-hand sites utilize lower coordination numbers (6 ± 2 vs. 7 ± 1), fewer protein ligands (4 ± 2 vs. 6 ± 1), and more water ligands (2 ± 2 vs. 1 ± 0) than EF-hand sites. The orders of ligand preference for non-EF-hand and EF-hand sites, respectively, were H₂O (33.1%) > side-chain Asp (24.5%) > main-chain carbonyl (23.9%) > side-chain Glu (10.4%), and side-chain Asp (29.7%) > side-chain Glu (26.6%) > main-chain carbonyl (21.4%) > H₂O (13.3%). Less formal negative charge was observed in the non-EF-hand than in the EF-hand binding sites (1 ± 1 vs. 3 ± 1). Additionally, over 20% of non-EF-hand sites had formal charge values of zero due to increased utilization of water and carbonyl oxygen ligands. Moreover, the EF-hand sites presented a narrower range of ligand distances and bond angles than non-EF-hand sites, possibly owing to the highly conserved helix–loop–helix motif. Significant differences between ligand types (carbonyl, side chain, bidentate) demonstrated that angles associated with each type must be classified separately, and the EF-hand side-chain Ca–O–C angles exhibited an unusual bimodal quality consistent with an Asp distribution that differed from the Gaussian model observed for non-EF-hand proteins. The results of this survey more accurately describe differences between EF-hand and non-EF-hand proteins and provide new parameters for the prediction and design of different classes of Ca²⁺-binding proteins. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Michael Kirberger, Xue Wang, and Hai Deng contributed equally to this article.     

Effects of suspended sediments,dissolved inorganic nutrients and salinity on fertilisation and embryo development in the coral <Emphasis Type="Italic">Acropora millepora</Emphasis> (Ehrenberg, 1834)

Exposure of coral reefs to river plumes carrying increasing loads of nutrients and sediments is a pressing issue for coral reefs around the world including the Great Barrier Reef (GBR). Laboratory experiments were conducted to investigate the effects of changes in inorganic nutrients (nitrate, ammonium and phosphate), salinity and various types of suspended sediments in isolation and in combination on rates of fertilisation and early embryonic development of the scleractinian coral Acropora millepora. Dose–response experiments showed that fertilisation declined significantly with increasing sediments and decreasing salinity, while inorganic nutrients at up to 20 μM nitrate or ammonium and 4 μM phosphate had no significant effect on fertilisation. Suspended sediments of ≥100 mg l⁻¹ and salinity of 30 ppt reduced fertilisation by >50%. Developmental abnormality occurred in 100% of embryos at 30 ppt salinity, and no fertilisation occurred at ≤28 ppt. Another experiment tested interactions between sediment, salinity and nutrients and showed that fertilisation was significantly reduced when nutrients and low concentrations of sediments co-occurred, although both on their own had no effect on fertilisation rates. Similarly, while slightly reduced salinity on its own had no effect, fertilisation was reduced when it coincided with elevated levels of sediments or nutrients. Both these interactions were synergistic. A third experiment showed that sediments with different geophysical and nutrient properties had differential effects on fertilisation, possibly related to sediment and nutrient properties. The findings highlight the complex nature of the effects of changing water quality on coral health, particularly stressing the significance of water quality during coral spawning time. Communicated by Environment Editor Professor Rob van Woesik     

Controls on chlorophyll-a in nutrient-rich agricultural streams in Illinois, USA

Nitrogen and phosphorus are the primary nutrients that affect water quality in streams in the midwestern USA and high concentrations of these nutrients tend to increase algal biomass. However, how nutrients interact with physical controls in regulating algal biomass is not well known in agricultural streams. Eighteen streams in east-central Illinois (USA) were sampled during June and September 2003 to analyze factors possibly regulating algal biomass. Additionally, two shaded and two non-shaded sites in the Embarras River in east-central Illinois were sampled intensively from June to December 2003. Both sestonic and periphytic chlorophyll-a (chl-a) were analyzed, and periphytic chl-a was assessed on natural substrata and unglazed ceramic tiles. Although high concentrations of nutrients were found in these streams (mean total P = 0.09–0.122 mg l⁻¹ and mean NO₃-N=4.4–8.4 mg l⁻¹), concentrations of sestonic chl-a were low among all sites and both sampling periods (<18 mg m⁻³, median values of 5 and 3 in June and September, respectively). Filamentous algae were an important component of the algal communities in streams with stable substrata. Periphytic chl-a was generally not related to the concentration of N or P in the water column, and in non-shaded streams periphyton appeared at times to be light-limited due to turbid water. Turbidity was found to be an important factor controlling chl-a on ceramic tiles across the 18 sites and for the Embarras River sites; chl-a decreased exponentially in concentration (132–0 mg m⁻²) as turbidity increased from 4 to 39 NTU (r ² = 0.80). In general, the interaction between hydrology and light (turbidity) likely controlled algal biomass in these nutrient-rich, agricultural streams.     

Effects of increases in salinity on phytoplankton in the Broadwater of the Myall Lakes, NSW, Australia

The Broadwater of the Myall Lakes system is highly susceptible to cyanobacterial bloom formation after heavy rain events. During prolonged low flow periods, saline intrusion from the lower Myall River increases salinity levels and effectively controls some bloom forming algal taxa. To assess the effect of low-to-moderate increases in salinity (up to 4 ppt) on phytoplankton chlorophyll a, cell abundance, diversity and assemblage structure, salinity enhancement experiments were conducted on Broadwater samples collected in June 2005 (salinity 1.5 ppt), October 2005 (4 ppt) and January 2006 (12 ppt). Natural phytoplankton assemblages were incubated in the laboratory for 10 days, under different treatments of salinity (no addition, +2 ppt, + 4 ppt) and nutrient conditions (no addition, excess N+P). The greatest impact of salinity enhancement in N+P enriched samples was observed in June (1.5–5.5 ppt); chlorophyll a was significantly reduced in samples with the highest salinity treatment, and the taxon most negatively affected by an elevation in salinity to 5.5 ppt was Anabaena circinalis. Taxonomic richness and diversity (Shannon–Wiener index) were unexpectedly significantly higher at 5.5 ppt than at 1.5 ppt. This result, in part, explains the observed significant differences in phytoplankton assemblage structure over this salinity range. In October, the main effect of elevating salinity levels from 4 ppt to 8 ppt was a reduction in the abundance of chlorophytes, particularly Scenedesmus. Phytoplankton samples that were collected when the lake salinity level was 12 ppt were little affected by salinity increases of 2 ppt and 4 ppt, most likely because field samples were already relatively high in salt content. We suggest that further investigations focus on phytoplankton responses to salinity under a range of nutrient regimes that are common to coastal lakes.     

Influence of Environmental Salinity on Messenger RNA Levels of Growth Hormone, Prolactin, and Somatolactin in Pituitary of the Channel Catfish (Ictalurus punctatus)

Pituitary growth hormone (GH), prolactin (PRL), and somatolactin (SL) messenger RNA levels in channel catfish (Ictalurus punctatus) were examined under various environmental and physiological conditions. Catfish were sampled following salinity challenge, during the winter (December) and spring or summer (April or July), and at different sizes (15–18 g, 620–664 g, and 956–1134 g). When catfish (956–1134 g) were transferred from freshwater to saline water containing 8 ppt NaCl, their plasma [Na⁺] increased significantly above values in the freshwater control group until they were transferred back to freshwater. Pituitary GH mRNA levels were low for the first 24 hours following transfer to saline water, but thereafter were significantly elevated above control values until the fish were transferred back to freshwater. Pituitary GH mRNA levels were highest in July and lowest in December. Growth hormone mRNA levels were also elevated in the size groups 15–18 g and 956–1134 g in July when compared with December values. Pituitary PRL mRNA levels increased for the first 24 hours following transfer to saline water (956–1134 g), but thereafter were significantly lower than control values until the fish were transferred back to freshwater. Pituitary PRL mRNA levels were highest in April and July and lowest in December, and were also elevated in the size groups 620–664 g and 956–1134 g. Pituitary SL mRNA levels were unaffected in catfish transferred to saline water; however, levels were significantly elevated in catfish of the 956–1134-g size group sampled in April when compared with December. These results suggest the involvement of GH in adaptation to brackish water and of PRL in adaptation to freshwater in the catfish, and seasonal and size-related differences in pituitary GH, PRL, and SL mRNA levels. Received May 17, 2000; accepted October 30, 2000     

Instability of the turbidity maximum in the macrotidal Geum River estuary, western Korea

In the low-salinity area of many macrotidal estuaries, through the combination of tidal pumping and estuarine circulation, an estuarine turbidity maximum (ETM) develops providing favorable conditions for various organisms. To investigate ecological roles of the ETM in East Asian estuaries, we conducted seasonal observations in the Geum (or Keum) River estuary, one of the representative macrotidal estuaries flowing into the Yellow Sea, from 2007 to 2008. The estuary was frequently filled with high-salinity (>10 PSU) and low-turbidity (<100 NTU) water under small or no freshwater discharge from a dam (ca. 8 km upstream from the river mouth). Brackish water was, however, completely pushed out of the estuary within a few hours after an intensive discharge in summer. Chlorophyll a (up to 50 μg l⁻¹) and pheophytin (up to 80 μg l⁻¹) were concentrated in a low-salinity (<1 PSU) and high-turbidity (up to 1000 NTU) area, indicating that the intensive discharge transported both living phytoplankton and resuspended detritus into the area. In contrast, a phytoplankton bloom (chlorophyll a, up to 100 μg l⁻¹) was observed at low salinities under little discharge in winter. The present study demonstrated an absence of the ETM suitable for estuarine-dependent organisms from the present Geum River estuary, indicating potential importance of adequate control of freshwater discharge for the formation and maintenance of the ETM.     

Long-term study of zooplankton in the estuarine system of Ribeira Bay,near a power plant (Rio de Janeiro,Brazil)

The structure of the zooplankton community in an estuary adjacent to the Admiral álvaro Alberto Nuclear Power Plant at Angra dos Reis, state of Rio de Janeiro, Brazil was studied from 2001 through 2005. At that time, the power plant had been operating for 20 years. The results were compared with a previous study in 1991–1993. The zooplankton was sampled 4 times a year, in vertical hauls using a 150 μm net, at two fixed points near the plant’s intake and discharge sites. Temperature, salinity, and chlorophyll a were measured. The water of Ribeira Bay is warm, with salinities typical of Coastal Water and more saline waters. Zooplankton density at the discharge site (Mean: 245,434 ind m⁻³, SD: 335,358 ind m⁻³) was higher than that at the intake site (Mean: 84,634 ind m⁻³, SD: 101,409 ind m⁻³). A total of 121 mesozooplankton taxa were recorded from 2001 to 2005. Copepoda constituted the most common taxon and comprised more than 57% of the total zooplankton, followed by cladocers and gastropod larvae. A seasonal zooplankton cycle was observed only during 2004; in other years, the plankton varied only between years. Overall mesozooplankton abundance at the discharge site was similar to levels reported from the inner zone of this estuary in 1991–1993. Surface temperature was the important factor structuring the zooplankton community at the discharge site. No effect on the mesozooplankton by passage through the condensers could be discerned, and no permanent negative influence on the plankton populations could be detected. Guest editors: U. M. Azeiteiro, I. Jenkinson & M. J. Pereira Plankton Studies     

Native bird breeding in a chronosequence of revegetated sites

Restoration of degraded landscapes through replantings of native vegetation has been proceeding in response to habitat loss and fragmentation and plummeting biodiversity. Little is known about whether the investments in ecological restoration have resulted in biodiversity benefits. We evaluated the potential of restored sites to support populations by assessing bird breeding activity. We surveyed 21 revegetated sites of various ages (9–111 years) in the box–ironbark region of Victoria, Australia. Sites differed in landscape context, patch features and in-site characteristics. The latter, including whether sites were grazed, amounts of fallen timber and numbers of remnant trees, were most important in affecting overall bird breeding activity. Patch-configuration (e.g., shape, area) was of secondary importance. Landscape context appeared to have little effect on bird breeding except for one species. While these results suggest that in-site habitat structure is the predominant driver, we caution against dismissing the importance of patch characteristics and landscape context for two reasons. First, the available sites covered a relatively small range of areas (<54 ha), and we could not provide a broad range of landscape-contextual contrasts given that we could only use existing plantings. Second, much of the breeding activity was by bird species known to be tolerant of smaller woodland areas or of the open countryside. We show that there is very little breeding activity in replantings by species that have declined dramatically in rank abundance between large ‘reference’ areas and fragmented landscapes. It seems likely that most replantings provide habitat configurations unsuited for dealing with declines of species most vulnerable to habitat loss and fragmentation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Soluble Reactive Phosphorus Transport and Retention in Tropical, Rainforest Streams Draining a Volcanic and Geothermally Active Landscape in Costa Rica. : Long-Term Concentration Patterns, Pore Water Environment and Response to ENSO Events

Soluble reactive phosphorus (SRP) transport/retention was determined at four sites in three rainforest streams draining La Selva Biological Station, Costa Rica. La Selva is located at the base of the last remaining intact rainforest transect from 30 m above sea level to 3000 m along the entire Caribbean slope of Central America. Steam SRP levels can be naturally high there due to regional, geothermal groundwater discharged at ambient temperature. Monitoring since 1988 has revealed distinctive long-term differences in background SRP and total P (TP) for three streams in close proximity, and identified the impact of ENSO (El Nino Southern Oscillation) events on SRP-enriched reaches. Mean interannual SRP concentrations (± standard deviation) were 89 ± 53μg/l in the Salto (1988–1996), 21 ± 39μg/l in the Pantano (1988–1998), and 26 ± 35μg/l in the Sabalo (1988–1996). After January, 1997 the separate upland-lowland contributions to discharge and SRP load were determined monthly in the Salto. SRP in Upper Salto was low (19 ± 8μg/l, 1997–2002) until enriched at␣the upland-lowland transition by regional groundwater. Mean SRP concentration in Lower␣Salto (108 ± 104μg/l) was typically highest February–April, the driest months, and lowest July–September, the wettest. SRP concentration was positively correlated to the inverse of discharge in Lower Salto when ENSO data were omitted (1992 and 1998–1999), but not in the Upper Salto, Pantano, or Sabalo. TP was positively correlated to the inverse of discharge in all three streams when ENSO data were omitted. High SRP springs and seeps along the Lower Salto contributed 36% of discharge but 85% of SRP export 1997–2001. Annual SRP flux from the total Salto watershed (1997–2001) averaged 2.9 kg/ha year, but only 0.6 kg/ha year from the Upper Salto. A dye tracer injection showed that pore water environments were distinctly different between Upper and Lower Salto. Upper Salto had high surface water–pore water exchange, high dissolved oxygen, low SRP, and low conductivity similar to surface water, and Lower Salto had low surface water–pore water exchange, low dissolved oxygen, high SRP, and high conductivity reflecting geothermal groundwater influence. SRP export from the Salto was controlled by regional groundwater transfer, which in similar volcanic settings could be a significant P source. However, ENSO events modified the SRP concentration in the Salto suggesting that long-term monitoring is required to understand underlying SRP dynamics and P flux to downstream communities.     

Osmoregulation in juvenile and adult white sturgeon,Acipenser transmontanus

Synopsis Blood samples from cannulated young adult (2.5–15 kg) white sturgeon, acclimated to San Francisco Bay water (24 ppt) had plasma values of 248.8 ± 13.5 mOsm kg⁻¹ H₂O, [Na⁺] = 125 ± 8.0 mEq 1⁻¹, [K⁺] = 2.6 ± 0.8 mEq 1⁻¹ and [CL⁻] = 122 ± 3.0 mEq 1⁻¹. Freshwater acclimated sturgeon had an osmolality of 236 ± 7, [Na⁺] = 131.6 + 4.4, [K⁺] = 2.5 ± 0.7 and [CL⁻] = 110.6 ± 3.6. Freshwater acclimated fish gradually exposed to sea water (increase of 5 ppt h⁻¹) had higher plasma osmolalities than did the bay water acclimated fish. These young adult sturgeon are able to tolerate transfer from fresh water to sea water as well as gradual transfer from sea water to fresh water. Plasma electrolytes in transferred fish are regulated, but tend to differ from long term acclimated fish at the same salinities. There is a gradual increase in the upper salinity tolerance (abrupt transfer) of juvenile white sturgeon with weight: 5–10 ppt for 0.4–0.9 g fish, 10–15 ppt for 0.7–1.8 g fish, and 15 ppt for 4.9–50.0 g fish. The ability of juveniles to regulate plasma osmolality is limited. The young adult fish are able to tolerate higher salinities (35 ppt) than juvenile sturgeon but probably are also characterized by low activity of the necessary ion exchange mechanisms in the gills which permit rapid adjustment of blood electrolytes with graduate change in external salinity.     

Spatio-temporal variations of the zooplankton abundance and composition in a West African tropical coastal lagoon (Grand-Lahou,Côte d’Ivoire)

Zooplankton constitutes a sensitive tool for monitoring environmental changes in coastal lagoons; however, the available information on zooplankton communities is not sufficient to optimize their rational management. The relationships between zooplankton distribution and environmental factors were studied in a tropical lagoon to test whether the indicator properties of zooplankton assemblages could be used to monitor water quality, in a context of expected eutrophication provoked by an increasing anthropogenic activity. Twenty-one (21) stations were sampled monthly from January to December 2004. The community was composed of 65 taxa including Copepoda, Rotifera, and Cladocera. Copepoda was the most abundant group (81% of total numbers). The main zooplankton species were Oithona brevicornis, Acartia clausi, and Brachionus plicatilis. The highest zooplankton abundance (171–175 ind. l⁻¹) was recorded during the long, dry season (February–April) and the lowest (40–45 ind. l⁻¹) during the rainy and the flood periods (June–July). At a spatial level, the lowest abundance was observed in the estuarine zone. During the dry seasons (December–April and August–September), marine zooplankton taxa were abundant near the channel of Grand-Lahou, and brackish water taxa dominated in the other sites. Multivariate analyses (Co-inertia) showed that the composition of zooplanktonic communities and their spatio-temporal variations were mainly controlled by salinity variations closely linked to the climatic and hydrological context. The role of the trophic state on zooplankton communities could not be clearly evidenced. Our results and a comparison with previous studies in the neighboring, highly polluted Ebrié Lagoon suggest that the ratio between Oithona and Acartia abundance could be used as biological indicator for the water quality. Handling editor: S. I. Dodson     

Combined effects of simulated tidal sea-level rise and salinity on seedlings of a mangrove species, Kandelia candel (L.) Druce

To investigate the effects of the simultaneous occurrence of salt stress and tidal sea-level rise on mangroves, potted Kandelia candel seedlings were treated under deep flooding (flooded 40 cm above the soil surface for 16 h per day, inundating the entire plant) and shallow flooding (flooded just above the soil surface for 8 h per day) at salinity levels of 5, 15, and 25 ppt over 14 months. Deep flooding enhanced stem elongations at all salinity levels but increased stem biomass only at 5 ppt. Deep flooding increased both leaf production and leaf fall; leaf biomass increased at 5 ppt, but decreased at 15 and 25 ppt. Biomass ratios of root/shoot (R/S) of deep flooding treatments were significantly lower than those of shallow flooding treatments. Under deep flooding, superoxide dismutase (SOD) activities did not show significant change between 5 and 15 ppt, but increased at 25 ppt. With increasing salinity level, peroxidase (POD) activities increased, and the difference between shallow and deep flooding was enhanced. Malonaldehyde (MDA) content significantly decreased at 25 ppt with 40 cm flooding, but was not affected by other treatments. These results demonstrated that the growth and physiological responses of K. candel seedlings under deep flooding conditions varied with salinity level; growth was enhanced at low salinity level but inhibited at high salinity level. It is therefore probable that K. candel will shift from downstream to upstream, where the influence of fresher river water resources will ameliorate the effects of increased salinities that accompany deeper tidal flooding in these mangrove ecosystems.     

Reversibility of Soil Productivity Decline with Organic Matter of Differing Quality Along a Degradation Gradient

In the highlands of Western Kenya, we investigated the reversibility of soil productivity decline with increasing length of continuous maize cultivation over 100 years (corresponding to decreasing soil organic carbon (SOC) and nutrient contents) using organic matter additions of differing quality and stability as a function of soil texture and inorganic nitrogen (N) additions. The ability of additions of labile organic matter (green and animal manure) to improve productivity primarily by enhanced nutrient availability was contrasted with the ability of stable organic matter (biochar and sawdust) to improve productivity by enhancing SOC. Maize productivity declined by 66% during the first 35 years of continuous cropping after forest clearing. Productivity remained at a low level of 3.0 t grain ha^-1 across the chronosequence stretching up to 105 years of continuous cultivation despite full N–phosphorus (P)–potassium (K) fertilization (120–100–100 kg ha⁻¹). Application of organic resources reversed the productivity decline by increasing yields by 57–167%, whereby responses to nutrient-rich green manure were 110% greater than those from nutrient-poor sawdust. Productivity at the most degraded sites (80–105 years since forest clearing) increased in response to green manure to a greater extent than the yields at the least degraded sites (5 years since forest clearing), both with full N–P–K fertilization. Biochar additions at the most degraded sites doubled maize yield (equaling responses to green manure additions in some instances) that were not fully explained by nutrient availability, suggesting improvement of factors other than plant nutrition. There was no detectable influence of texture (soils with either 11–14 or 45–49% clay) when low quality organic matter was applied (sawdust, biochar), whereas productivity was 8, 15, and 39% greater (P < 0.05) on sandier than heavier textured soils with high quality organic matter (green and animal manure) or only inorganic nutrient additions, respectively. Across the entire degradation range, organic matter additions decreased the need for additional inorganic fertilizer N irrespective of the quality of the organic matter. For low quality organic resources (biochar and sawdust), crop yields were increasingly responsive to inorganic N fertilization with increasing soil degradation. On the other hand, fertilizer N additions did not improve soil productivity when high quality organic inputs were applied. Even with the tested full N–P–K fertilization, adding organic matter to soil was required for restoring soil productivity and most effective in the most degraded sites through both nutrient delivery (with green manure) and improvement of SOC (with biochar).     

Cloning and expression of three peptide-linked β2-microglobulin molecules in <Emphasis Type="Italic">Escherichia coli</Emphasis> with an isocaudamer technique

The application of the peptide-linked β2-microglobulin (β2m) strategy is limited in some cases due to the incompatibility between the sequences of the peptides and the restriction sites of the plasmid vectors. An isocaudamer technique was adapted to overcome this restriction. Three peptide-linked β2m genes, HBc_18–27-hβ2m gene, OVA_257–264-mβ2m gene and HER2/neu_369–377-mβ2m gene, were inserted into the pET28a vectors with this technique. The corresponding proteins were expressed in Escherichia coli with yields of over 50 mg/l culture and purities of over 80%. This strategy facilitates the construction of peptide-linked β2m molecules and will simplify the preparation of major histocompatibility complex-peptide complexes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.