Magnesium and strontium compositions of recent symbiont-bearing benthic foraminifera

Minor and trace elements in foraminiferal carbonates are potential paleo-proxies of climate, nutrient and seawater composition. There are very few reports of trace element composition of symbiont-bearing, larger foraminifera that are known to be important constituents of shallow-marine, modern and ancient carbonates. In this paper we examine the range of variation in Mg and Sr content of Recent species of these foraminifera from a lagoon of Lakshadweep Atoll (Indian Ocean) and Akajima Islands, Japan. Two hyaline species, Amphistegina lessonii and Neorotalia calcar,and two porcellaneous species, Amphisorus hemprichii and Marginopora vertebralis were collected live from Lakshadweep islands. Mg / Ca in these foraminifera is of an order of magnitude higher than the values reported for planktonic and symbiont-free benthic foraminifera. The Sr / Ca values are, however, comparable with the reported values in other foraminiferal taxa and they are found to vary within a narrow range. Electron-probe micro-analysis of three symbiont-bearing benthic species indicates spatial heterogeneity of high orders in Mg / Ca composition in all the species. The annual variation in temperature and pH of the lagoon water cannot explain the observed amplitude of the compositional variation. The photosynthesis and respiration of the symbionts and host foraminifera are possibly the major cause of compositional heterogeneity in individual tests, as has also been recently postulated for symbiont-bearing planktonic foraminiferal species. It highlights the need to isolate biological factors and necessitates species-specific paleotemperature scale in paleoclimatic analysis. We also analyzed δ¹⁸O, δ¹³C, Ca, Mg and Sr in carefully dissected chambers of a reef-dwelling, porcellaneous benthic foraminifer, Marginopora kudakajimaensis, collected live in four seasons. A moderate positive correlation is observed between Mg / Ca and temperature. However, large inter- and intra-test variation in Mg limits the precision of Mg / Ca as palaeotemperature proxy. The Sr / Ca of the test calcite is unrelated to temperature of the sea water. The δ¹³C of M. kudakajimaensis does not correlate with δ¹⁸O, Mg / Ca or Sr / Ca.     

Benthic foraminifera and trace metal distribution: a case study from the Burullus Lagoon,Egypt

Benthic foraminifera are widely used to detect the health of their habitat, where they are very sensitive to even slight variations in the ecosystem. Therefore, the main objectives of this study are to examine the benthic foraminiferal assemblages in the sediments of Burullus Lagoon, evaluate the pollution levels and deduce the impact of trace metals on foraminifera. The continuous discharge of trace metals from agricultural, industrial and domestic sources into the lagoon may lead to a severe environmental problem. The concentrations of Mn, Cu, Cd, Zn and Pb within the sediments were measured. Recently, the assessment of contamination is principally based on the contamination indices which provide fast and simple quantitative values on the degree of pollution in a given aquatic environment. Thus, some indices, including the contamination factor, the degree of contamination, pollution load index, geoaccumulation index, ecological risk factor and potential ecological risk index are applied in this investigation. Based on the contamination factors, the sediments are very highly contaminated with Cd, considerably to very highly contaminated with Cu and Zn, moderately contaminated with Mn, low to moderately contaminated with Pb. All sites display very high values for the degree of contamination. Moreover, the values of the pollution load index are higher than 1, indicating that the lagoon is polluted. Depending on the geoaccumulation index, the contaminants are arranged as follows Cd > Zn > Cu > Mn > Pb. It is clear that Cd is the main contributor to the ecological risk factor in Burullus Lagoon. Concerning the richness of the foraminiferal assemblages, it fluctuates between 1–5 species per sample. Because of its higher tolerance to extreme conditions (changes in salinity and pollution), Ammonia tepida is the most abundant species. The occurrence of rare living individuals (25) is restricted only to sites close to El-Boughaz Inlet where higher salinity and lower levels of pollution are recorded. The same trend of distribution is shown by Cribroelphidium excavatum and miliolids, where they occur at sites with higher salinities. The occurrence of test deformities in all the studied sites may be related to the response of benthic foraminifera to trace metal. The forms of deformation include spiroconvex, reduced chambers, twisted tests, twinning, additional chamber and complex forms. The deformation depends on the nature of pollutants. Twinning and reduced chambers are the most dominant forms in areas close to the agricultural drainage (southern drains), while complex forms are abundant in areas close to industrial drainage (El-Gharbia drain). Thus, salinity and pollution may be the most regulatory factors controlling the distribution of foraminifera. This investigation confirmed the role of benthic foraminifera as a good ecological indicator in Burullus Lagoon.     

Influences of sedimentation and hydrodynamics on the spatial distribution of Alexandrium catenella/tamarense resting cysts in a shellfish farming lagoon impacted by toxic blooms

Since resting cysts are a potential seeding source for blooms, the presence of these cysts in sediments is a marker of an established population for a number of harmful algal species. The spatial patterns of cyst density in relation to sediment characteristics and hydrodynamics are still largely misunderstood. This study investigated the spatial distribution of resting cysts belonging to the Alexandrium tamarense species complex (Dinophyceae) in sediments of a Mediterranean coastal lagoon (Thau Lagoon, France). This lagoon, hosting shellfish farming, is regularly impacted by toxic Alexandrium catenella blooms. The average cyst density across the whole lagoon was rather low, <20 cysts g⁻¹ of dry sediment (DS). However, densities varied widely among sampled stations, with the highest density (∼440 cysts g⁻¹ DS) recorded in a shallow cove named Crique-de-l’Angle, which is the only area where dense blooms of A. catenella and A. tamarense have been recorded in the years preceding this survey. An analysis using spatial autoregressive models demonstrated that cyst densities were highly spatially autocorrelated (indicating that close stations tended to have more similar cyst densities) with accumulation sites. With respect to sediment characteristics (5 granulometric fractions <2 mm and biochemical components), the highest densities were found in silty sediments containing high proportions of water and organic matter. Nevertheless, the linkage between cyst density and sediment structure was not always verified; this reflected the influence of hydrodynamics on the sedimentation of cysts and sediment particles, and on the dispersal of cysts away from the bloom area by wind-induced currents, suggesting that hydrodynamics was responsible for the spatially autocorrelated distribution of cyst densities.     

Changes in abundances of Alexandrium tamarense resting cysts after the tsunami caused by the Great East Japan Earthquake in Funka Bay,Hokkaido, Japan

The 2011 Great East Japan Earthquake and the subsequent huge tsunami greatly affected both human activity and the coastal marine ecosystem along the Pacific coast of Japan. The tsunami also reached Funka Bay in northern Japan and caused serious damage to the scallop cultures there, and this tsunami was believed to have affected the coastal environments in the bay. Therefore, we investigated the changes in the spatial abundance and distribution of the toxic dinoflagellates Alexandrium tamarense cysts before the tsunami (August 2010) and after the tsunami (May 2011, August 2011, May 2012 and August 2012) in the bay. Further, monthly sampling was conducted after the tsunami to identify seasonal changes of Alexandrium catenella/tamarense cysts and vegetative cells. Significant increases were observed in the populations of A. catenella/tamarense cysts, comparing the abundances before the tsunami (in August 2010; 70 ± 61 cysts g⁻¹ wet sediment) to those just after it (in May 2011; 108 ± 84 cysts g⁻¹ wet sediment), and both A. tamarense bloom (a maximum density was 1.3 × 10³ cells L⁻¹) and PSP (Paralytic Shellfish Poisoning) toxin contamination of scallops (9.4 mouse unit g⁻¹ was recorded) occurred in the bay. Seasonal sampling also revealed that the encystment of A. tamarense and the supply of the cysts to bottom sediments did not occur in the bay from September to April. These results strongly suggested that the mixing of the bottom sediments by the tsunami caused the accumulation of the toxic A. tamarense cysts in the surface of bottom sediment through the process of redeposition in Funka Bay. Moreover, this cyst deposition may have contributed to the toxic bloom formation as a seed population in the spring of 2011.     

Multiannual Chattonella subsalsa Biecheler (Raphidophyceae) blooms in a Mediterranean lagoon (Santa Giusta Lagoon,Sardinia Island,Italy)

Recurrent blooms of Chattonella subsalsa (Raphidophyceae) were associated with fish kills in Santa Giusta Lagoon (Mediterranean Sea). This study investigated the population dynamics of C. subsalsa and its relationship with environmental and meteorological conditions, using multiannual ecological data (1990–2016). In addition, for the first time, this study examined the presence of C. subsalsa cysts in lagoon sediments. The species was first detected in Santa Giusta Lagoon in July 1994. Bloom events coinciding with fish kills were recorded in 1994, 1998, 1999, and 2010. The timing and dynamics of C. subsalsa blooms and fish kills varied over the examined period. Presence of C. subsalsa was strongly influenced by temperature, especially in the early years of the series (1990–2002). Temperature control may have been lesser important in the more recent years, when higher temperature may have generated continuative suitable conditions for C. subsalsa affirmation, especially in July. Thus, the variations in the availability of food (via autotrophy and/or mixotrophy) could be one of the control keys on the proliferation of this species in the future in SG. Cysts of C. subsalsa were present in lagoon sediments at abundances ranging 200–2000 cysts g⁻¹ wet sediment. This study is among a few that have examined C. subsalsa population dynamics and bloom events in the field over a long time period. Findings from this study contribute to a better understanding of C. subsalsa bloom development, by identifying environmental and meteorological variables that may promote blooms of this species in the Santa Giusta Lagoon.     

Foraminiferal assemblage indices: A comparison of sediment and reef rubble samples from Conch Reef,Florida, USA

Benthic foraminiferal assemblages are increasingly utilized as indicators of water and sediment quality in coastal-marine environments. Most reef-dwelling foraminifers live on firm substrata such as reef or phytal surfaces, while most assessments have examined assemblages from sediments. This case study compared relative abundances of total foraminiferal-shell assemblages between sediment and phytal/rubble samples collected from one reef within one week. A total of 117 species within 72 genera were identified, with the same taxa in both sample sets in different proportions. Larger benthic foraminifers and some agglutinated taxa were concentrated about 1.5–3 fold in sediment samples, while nearly two-thirds of small, fragile shells were lost. Several common indices were compared, including Taxonomic Richness (number of genera), Shannon (H), Simpson's (D) and Fisher (α) diversity indices, Evenness (E), and the FORAM Index (FI). Highly significant differences (p < 0.001) between shell assemblages from 13 sets of phytal/rubble substrata and sediments were found in mean number (± standard deviation) of genera (49 ± 4 vs. 34 ± 10) and mean FI (5.6 ± 0.8 vs. 3.6 ± 0.4); both reflecting greater relative abundances of smaller foraminifers in the rubble samples. Fisher diversity was marginally significant (p = 0.05); other indices showed no significant differences between sample types. Although assessment of total assemblages is substantially less costly than distinguishing between specimens that were live or dead when collected, many researchers report those distinctions. The results of our study provide insight that can assist interpretations of studies that use live assemblages to calculate the FI, rather than total assemblages for which it was originally developed.     

Alexandrium pacificum Litaker sp. nov (Group IV): Resting cyst distribution and toxin profile of vegetative cells in Bizerte Lagoon (Tunisia,Southern Mediterranean Sea)

A high spatial resolution sampling of Alexandrium pacificum cysts, along with sediment characteristics (% H₂O, % organic matter (OM), granulometry), vegetative cell abundance and environmental factors were investigated at 123 study stations in Bizerte Lagoon (Tunisia). Morphological examination and ribotyping of cells obtained from a culture called ABZ1 obtained from a cyst isolated in lagoon sediment confirmed that the species was A. pacificum. The toxin profile from the ABZ1 culture harvested during exponential growth phase was simple and composed of the N-sulfocarbamoyl toxins C1 (9.82 pg toxin cell⁻¹), the GTX6 (3.26 pg toxin cell⁻¹) and the carbamoyl toxin Neo-STX (0.38 pg toxin cell⁻¹). The latter represented only 2.8% of the total toxins in this strain.High abundance of A. pacificum cysts correlated with enhanced percentages of water and organic matter in the sediment. In addition, sediment fractions of less than 63 μm were examined as a favorable potential seedbed for initiation of future blooms and outbreaks of A. pacificum in the lagoon. A significant difference in the cyst distribution pattern was recorded among the lagoon's different zones, with the higher cyst abundance occurring in the inner waters. Also, no correlation due to the specific hydrodynamics of the lagoon was observed in the spatial distribution of A. pacificum cysts and vegetative cells.     

Macrophytes in the anthropic constructions of the Venice littorals and their ecological assessment by an integration of the “CARLIT” index

A check-list of the macroalgae which colonize the artificial structures “dykes” formed by limestone blocks, placed between the northern Adriatic Sea and the Venice Lagoon to protect the wide sea inlets of Lido and Malamocco, the stone breakwaters and the submerged reefs parallel and perpendicular to the sea coastline of the Lido island “Murazzi” is presented. Macroalgae have been sampled monthly during one-year period (February 2007–January 2008) both in the lagoon inlets and along the marine coast. Flora was represented by 213 taxa: 61 Chlorophyta, 114 Rhodophyta, 38 Ochrophyta (37 Phaeophyceae, 1 Xanthophyceae), with the richest and luxuriant vegetation in the lagoon inlet areas. The application of the Rhodophyta/Chlorophyta (R/C) index and the Expert-Macrophyte Quality Index (E-MaQI) highlighted the “High” ecological status (EQR > 0.9) of the lagoon inlet areas.As E-MaQI is not applicable in marine areas, an adaptation of CARLIT to the anthropic structures of the north-western coasts of the northern Adriatic Sea and its integration with the dominant taxa is proposed.The application of the revised index to the Lido dykes and breakwaters placed along the marine littorals shows “Moderate” conditions.     

Brevetoxin persistence in sediments and seagrass epiphytes of east Florida coastal waters

A bloom of Karenia brevis Davis developed in September 2007 near Jacksonville, Florida and subsequently progressed south through east Florida coastal waters and the Atlantic Intracoastal Waterway (ICW). Maximum cell abundances exceeded 10⁶ cells L⁻¹ through October in the northern ICW between Jacksonville and the Indian River Lagoon. The bloom progressed further south during November, and terminated in December 2007 at densities of 10⁴ cells L⁻¹ in the ICW south of Jupiter Inlet, Florida. Brevetoxins were subsequently sampled in sediments and seagrass epiphytes in July and August 2008 in the ICW. Sediment brevetoxins occurred at concentrations of 11–15 ng PbTx-3 equivalents (g dry wt sediment)⁻¹ in three of five basins in the northern ICW during summer 2008. Seagrass beds occur south of the Mosquito Lagoon in the ICW. Brevetoxins were detected in six of the nine seagrass beds sampled between the Mosquito Lagoon and Jupiter Inlet at concentrations of 6–18 ng (g dry wt epiphytes)⁻¹. The highest brevetoxins concentrations were found in sediments near Patrick Air Force Base at 89 ng (g dry wt sediment)⁻¹. In general, brevetoxins occurred in either seagrass epiphytes or sediments. Blades of the resident seagrass species have a maximum life span of less than six months, so it is postulated that brevetoxins could be transferred between epibenthic communities of individual blades in seagrass beds. The occurrence of brevetoxins in east Florida coast sediments and seagrass epiphytes up to eight months after bloom termination supports observations from the Florida west coast that brevetoxins can persist in marine ecosystems in the absence of sustained blooms. Furthermore, our observations show that brevetoxins can persist in sediments where seagrass communities are absent.     

Pollution characteristics of mercury (Hg) in surface sediments of major basins,China

To investigate the pollution status and potential pollution risk of mercury (Hg) in China, surface sediment samples were collected from eight hundred and eighty-one sites, including ten major basins (Songhua River Basin (SRB), Liao River Basin (LRB), Hai River Basin (HRB), Yellow River Basin (YRB), Huai River Basin (HuRB), Yangtze River Basin (YtRB), Pearl River Basin (PRB), Southeastern River Basin (SeRB), Southwestern River Basin (SwRB) and Northwestern River Basin (NwRB)). Results showed that Hg concentrations in sediments of ten basins in China ranged from 0.001 to 8.800 mg/kg, with average ± S.D. value of 0.274 ± 0.675 mg/kg, which was obviously higher than Chinese soil background value (0.038 mg/kg) and Chinese sediment background value (0.040 mg/kg). The mean Hg concentration of ten basins decreased in the order of HRB > YtRB > SRB > PRB > HuRB > SwRB > YRB > SeRB > LRB > NwRB. Moreover, it was found that the Hg concentrations in the sediments of LRB, YtRB, PRB, SeRB and SwRB were partly driven by their total organic carbon (TOC) contents, while the effect of pH on the distribution of Hg was not obvious. The Hg concentration data were also compared with those got in other periods (1994–2015) to obtain the general variation tendency of Hg level. It was recorded that Hg concentrations in HRB have remained on high levels for a long history, while Hg contamination situation in YRB after 2004 has potentially turned to be better. The results of pollution assessment by sediment quality assessment guidelines (SQGs), contamination factor (CF), geoaccumulation index (I_geo) and potential ecological risk (E_i) suggested that YRB and HRB were the most seriously polluted river basins among the ten basins. It is urgent of constructing SQGs in China to scientifically evaluate the Hg pollution in the future.     

New Middle Permian foraminifers (Chitralinidae) from the Karakaya Complex,in northwestern Turkey

One new foraminiferal genus, Rectoformata gen. nov., with two new species, has been described from a Permian limestone block in the Karakaya Complex in the South of the Balya district (Balikesir, northwestern Turkey). The type species of Rectoformata, Rectoformata tekini sp. nov., is characterized by a quadrangular transverse section having a calcareous microgranular wall with fine alveolar structures, whereas Rectoformata acari sp. nov. is recognized by a pentagonal transverse section having a calcareous microgranular wall with fine alveolar structures. The age of the described taxa is assigned as Midian ( = Capitanian) based on the association with small foraminifers and fusulinids. These new taxa are included in the family Chitralinidae, which is emended herein.     

Methane-induced early diagenesis of foraminiferal tests in the southwestern Greenland Sea

Planktic and epibenthic foraminiferal δ¹³C records at Site PS62/015-3 (southwestern Greenland Sea) reveal a series of transient events of extreme ¹³C depletion down to − 6‰ during the period 90–40 ka. Scanning electron microscope studies of the ultrastructures of foraminiferal tests suggest that ¹³C depleted specimens are affected by some 10–20% overgrowth by authigenic calcite contributing to the light δ¹³C signal. Incremental-leaching experiments and census counts of pristine versus overgrowth-affected specimens show that the ¹³C depleted foraminiferal tests incorporate a primary δ¹³C signature most likely ranging from + 1‰ to − 1.7‰ and a post-depositional δ¹³C signature around − 17‰ to − 19.5‰. Extremely low values of productivity and organic carbon in Late Quaternary sediments along the east Greenland margin preclude organic matter as potential source of the isotopically light carbon. In contrast, thermal instability of clathrates and subsequent aerobic oxidation of (highly ¹²C enriched) methane in pore and ocean water provide a compelling mechanism to account for the negative δ¹³C excursions of both primary and post-depositional carbonates. Here, pore water methane may have led to a supersaturation of ¹³C depleted bicarbonate and precipitation of isotopically light authigenic calcite on and in foraminiferal tests, a feature that may serve as a tracer to former sites of clathrate destabilization.     

Variability of soil carbon sequestration capability and microbial activity of different types of salt marsh soils at Chongming Dongtan

Variations in the soil carbon sequestration capability of different types of salt marsh soils at Chongming Dongtan and its influencing factors were studied by analyzing the soil organic carbon (SOC) content, organic matter input and microbial activities. The results indicated that the total SOC content at Area A (southeast of Dongtan, sandy soil with Phragmites communis) was only 46.11% of that of Area B (northeast of Dongtan, clay soil with mixed P. communis and Spartina alterniflora) (P = 0.000 < 0.05), but their organic matter input per year was almost identical. These findings implied that Area B had a lower output of SOC. The microbial biomass at Area A was 3.83 times greater than that at Area B (P = 0.049 < 0.05); the soil catalase and invertase activities at Area A, which were related to carbon metabolism, were 60.31% (P = 0.006 < 0.05) and 34.33% (P = 0.021 < 0.05) higher than at Area B, respectively; and the soil respiration at Area A was also higher than at Area B. These findings implied that the microbial activities at Area A were greater than those at Area B, and therefore the carbon metabolism was rapid, resulting in increased SOC output at Area A. Increased water content and salinity in the clay soil at Area B may inhibit the microbial activities, thereby reducing the decomposition of the organic matter and enhancing carbon sequestration. In addition, some artificial measures for controlling spread of S. alterniflora at Area B (mowing/digging and tillage (M + D); mowing/digging and tillage/waterlogging (M + D + W)) were found to generally improve the microbial activity of soil, thereby increasing SOC output. However, when the two different physical controlling modes were compared, the SOC and microbial activities of the soil subjected to the M + D + W treatment were relatively high and low, respectively, due to waterlogging restraining the microbial metabolism. These findings indicated that the difference in microbial activities was the important factor leading to variability in the SOC sequestration capability between Areas A and B. Additionally, with the exception of soil texture and vegetation types, environmental conditions and artificial turbulence also influenced microbial activities of soil, and hence SOC output and organic carbon sequestration capability.     

The Biological Sediment Tolerance Index: Assessing fine sediments conditions in Oregon streams using macroinvertebrates

Fine sediments in excess of natural background conditions are one of most globally common causes of stream degradation, with well documented impacts on aquatic communities. The lack of agreement on methods for monitoring fine sediments makes it difficult to share data, limiting assessments of stream conditions across jurisdictions. We present a model that circumvents these limitations by inferring fine sediments in Oregon streams through sampling of macroinvertebrates. Tolerances to fine sediments (<0.06 mm diameter) were calculated for 240 macroinvertebrate taxa, from a calibration dataset of 446 sites across Oregon, as well as an independent validation dataset of 50 samples. Weighted averaging methods were used to infer fine sediment levels in streams by weighting the tolerances of modeled taxa observed in a sample by their abundances. The final model, the Biological Sediment Tolerance Index (BSTI), showed a strong relationship to measured fine sediments (calibration r² = 0.49, validation r² = 0.58). Root-mean-squared-error was small in the calibration dataset (2% fines), but larger in the validation dataset (14% fines). Repeatability was assessed by examining variability in BSTI at 14 sites across Oregon. Because field methods for sampling macroinvertebrates are standardized across resource agencies in Oregon and the responses of macroinvertebrates represent the actual effects of fine sediments on stream ecosystems, the BSTI may offer water resource managers’ a cost-effective method for assessing fine sediment conditions in their ongoing efforts to improve water quality across the state.     

Growth responses of Zostera capricorni to estuarine sediment conditions

This study comprised (1) a field survey of intertidal seagrass (Zostera capricorni) biomass, cover and photosynthetic potential and sediment characteristics at a range of contrasting sites in three New Zealand harbours, and (2) a microcosm experiment comparing plant responses to sediments from extant versus historical seagrass sites. The field survey showed that the sediment physico-chemical characteristics were generally consistent with the limited previous reports for Zostera environments, although the total P concentration range was higher (0.08–0.72 mg P g⁻¹). Overall, 52% of variation in seagrass cover was explained by sediment water content (R = 0.54) and organic content (R = −0.56). Twenty-two percent of variation in seagrass biomass was explained by sediment total P and redox potential (both R = −0.35). Intra-harbour seagrass–sediment relationships were more significant (explaining up to 82% of plant variation) but harbour-specific. In the microcosm experiment, threefold higher Z. capricorni biomass was maintained on extant than historical sediments but not conclusively linked to measure sediment characteristics. Overall, the results of this study demonstrate that significant relations can exist between estuarine sediment conditions and Z. capricorni growth responses, and suggest that detrimental change in sediment conditions may be a contributing factor in seagrass decline.     

Faunal utilization of constructed intertidal oyster (Crassostrea rivularis) reef in the Yangtze River estuary,China

An intertidal oyster reef (～260 ha) was created by planting hatchery-reared seed oysters (Crassostrea rivularis) on an artificial concrete modular reef in the Deepwater Navigation Channel Regulation Project of the Yangtze River estuary. We examined the development of reef communities (oyster, barnacle and motile epibenthic macrofauna), characterized nekton use and assessed the habitat value of the constructed reef. The C. rivularis oyster population showed a rapid exponential increase with time and reached maximum density (3410 ± 241 ind./m²) and biomass (3175 ± 532 g/m²) after one year of restoration. The barnacle Balanus albicostatus was the most abundant sessile macrofauna and had a significantly greater density in the high intertidal zone than in the low intertidal zone (P < 0.05). The reef also supported diverse motile epibenthic macrofauna (11 mollusks, 11 crustaceans, 4 annelids and 2 fishes), and the reef-associated communities were numerically dominated by Neanthes japonica, Perinereis aibuhitensis, Nerita yoldi and Littorinopsis intermedia. A total of 50 nekton species (31 fishes, 9 shrimps and 10 crabs) utilized the constructed intertidal oyster reef, and grass shrimp Palaemon spp. dominated the nekton communities in term of abundance. Since the constructed intertidal oyster reef supports a variety of reef communities and abundant nektons, it should be recognized as an important and protective fish habitat in the Yangtze River estuary.     

Expansion of harmful brown tides caused by the pelagophyte,Aureoumbra lagunensis DeYoe et Stockwell,to the US east coast

Brown tides caused by the pelagophyte Aureoumbra lagunensis DeYoe et Stockwell have formed ecosystem disruptive algal blooms in shallow lagoons of Texas (TX), USA, for more than two decades but have never been reported elsewhere. During the summer of 2012, a dense brown tide occurred in the Mosquito Lagoon and northern Indian River Lagoon along the east coast of Florida (FL), USA. While chlorophyll a levels in this system have averaged 5 μg L⁻¹ during the past two decades, concentrations during this brown tide reached ∼200 μg L⁻¹. Concurrently, levels of nitrate were significantly lower than average and levels of dissolved organic nitrogen were significantly higher than average (p < 0.001 for both). Sequences of the 18S rRNA gene of the bloom community and of single cell isolates were identical to those of Aureoumbra lagunensis DeYoe et Stockwell from TX. The A. lagunensis brown tide in FL bloomed to densities exceeding 10⁶ cells mL⁻¹ (quantified with a species-specific immuno-label) from July through September, began to dissipate in October, but maintained densities exceeding 10⁵ cells mL⁻¹ in some regions through December of 2012. The decline of the bloom was associated with near-hypoxic conditions and more than 30 fish kills reported within the Mosquito Lagoon in September 2012, a number far exceeding all prior monthly reports in this system dating to 1996. Wild northern quahog populations (a.k.a. hard clam, Mercenaria mercenaria) suffered mass die offs during the brown tide and eastern oysters (Crassostrea virginica) that settled during 2012 were significantly smaller than prior years. Clearance rates of hard clams and eastern oyster were significantly reduced in the presence of Mosquito Lagoon bloom water and A. lagunensis monocultures isolated from the Mosquito Lagoon at densities of ∼10⁶ cells L⁻¹. The expansion of harmful brown tides caused by A. lagunensis to these estuaries represents a new threat to the US southeast coast.     

Growth responses of Zostera capricorni to estuarine sediment conditions

This study comprised (1) a field survey of intertidal seagrass (Zostera capricorni) biomass, cover and photosynthetic potential and sediment characteristics at a range of contrasting sites in three New Zealand harbours, and (2) a microcosm experiment comparing plant responses to sediments from extant versus historical seagrass sites. The field survey showed that the sediment physico-chemical characteristics were generally consistent with the limited previous reports for Zostera environments, although the total P concentration range was higher (0.08–0.72 mg P g⁻¹). Overall, 52% of variation in seagrass cover was explained by sediment water content (R = 0.54) and organic content (R = −0.56). Twenty-two percent of variation in seagrass biomass was explained by sediment total P and redox potential (both R = −0.35). Intra-harbour seagrass–sediment relationships were more significant (explaining up to 82% of plant variation) but harbour-specific. In the microcosm experiment, threefold higher Z. capricorni biomass was maintained on extant than historical sediments but not conclusively linked to measure sediment characteristics. Overall, the results of this study demonstrate that significant relations can exist between estuarine sediment conditions and Z. capricorni growth responses, and suggest that detrimental change in sediment conditions may be a contributing factor in seagrass decline.     

Stable oxygen and carbon isotopes of live benthic foraminifera from the Bay of Biscay: Microhabitat impact and seasonal variability

We determined the stable oxygen and carbon isotopic composition of live (Rose Bengal stained) benthic foraminifera (> 150 μm size fraction) of seven taxa sampled along a downslope transect between 140 to 2000 m water depth in the Bay of Biscay. At the five stations, Hoeglundina elegans, Cibicidoides pachydermus, Uvigerina peregrina, Uvigerina mediterranea preferentially occupy shallow infaunal niches, whereas Melonis barleeanus and Uvigerina elongatastriata occupy an intermediate infaunal microhabitat, and Globobulimina spp. live in a deep infaunal niche close to the zero oxygen boundary.When compared with δ¹⁸O values of calcite formed in equilibrium with bottom waters, U. peregrina forms its test in close equilibrium with bottom water δ¹⁸O. All other foraminiferal taxa calcify with a constant offset to calculated equilibrium calcite. There is no systematic relationship between the foraminiferal microhabitat depth and the Δδ¹⁸O between foraminiferal and equilibrium calcite. We calculated correcting factors for the various taxa, which are needed for constructing multispecies-based oxygen isotope records in paleoceanographic studies of the study area.The δ¹³C values of foraminiferal taxa investigated in this study do neither record bottom water δ¹³C_DIC in a 1 : 1 relationship nor with a constant offset, but appear to be mainly controlled by microhabitat effects. The increase of δ¹³C values of shallow infaunal taxa with increasing water depth reflects the decrease of the exported flux of organic carbon along the bathymetric transect and early diagenetic processes in the surface sediment. This is particularly the case for the shallow infaunal U. peregrina. The δ¹³C values of deep infaunal Globobulimina spp. are much less dependent on the exported organic matter flux. We suggest that the Δδ¹³C between U. peregrina and Globobulimina spp. can shed light on the various pathways of past degradation of organic detritus in the benthic environments.At a station in 550 m water depth, where periodic eutrophication of sediment surface niches was demonstrated previously, we performed a two-year seasonal survey of the isotopic composition of foraminiferal faunas. No marked seasonal changes of the stable carbon isotopic composition of shallow, intermediate and deep infaunal foraminiferal taxa were observed. Thus, the δ¹³C values of foraminiferal individuals belonging to the > 150 μm fraction may result from rather long-term calcification processes lasting for several weeks or months, which limit the impact of ephemeral ¹²C enrichment of shallow infaunal niches on the isotope chemistry of adult individuals during eutrophic periods. Only highly opportunistic taxa reproducing or calcifying during phytoplankton bloom periods and the subsequent deposits of phytoplankton remains in the benthic environment may exhibit a particularly low δ¹³C, indicative of such short productive periods.     

Spatial and temporal changes in the microbial community in an anaerobic swine waste treatment lagoon

Microorganisms are central to both the beneficial (organic degradation, nutrient removal, biogas production) and detrimental (odor production, pathogen contamination) effects of swine waste storage systems. In this study, both quantitative (real-time polymerase chain reaction) and qualitative (denaturing gradient gel electrophoresis, cloning, sequence analysis) molecular analyses were used to track spatial and temporal changes in the microbial community of swine slurry from a 0.4 ha anaerobic lagoon. The lagoon, located in a region of western Kentucky which has a humid, subtropical environment, was sampled on a monthly basis (n = 10) over a period of one year at four different depths (top, 51 cm from the top, 152 cm from the top, and bottom >198 cm). The concentration and diversity of Bacteroides sp. was seasonal (up to 90% decrease between March and June). Hespellia sp. and other clostridial species, on the other hand, were endemic in the slurry (concentrations up to 1.0 × 10⁷ cells mL^?1 slurry) regardless of time of the year or lagoon depth. Results suggest that there were seasonal effects on the microbial community in the swine lagoon, while the effect of depth was not as pronounced. Seasonal changes in the microbial community in stored wastes may be (directly or indirectly) correlated with changes in malodor emissions from lagoons.