Agroecological zone-specific fish culture systems in Tien Giang province, Mekong delta, Vietnam.

The Rural Extension for Aquaculture Development (READ) project, which operated in Cambodia and Vietnam from 1998 to 2001, confirmed that improved fish production could make significant contributions to the nutrition, well-being and cash income of poor and marginal rural households with small ponds. READ tested a sustainable approach for small-scale aquaculture extension. Farmer problems and needs were first identified for (i) flood prone, (ii) limited water exchange or saline intrusion, (iii) inland and (iv) acid sulphate agro-ecological zones. Farmer-managed on-farm trials to test technologies under appropriate social conditions, on-farm research and on-station research were then conducted, leading to the identification and development of agro-specific aquaculture technologies appropriate for poor and marginal households. Technologies were disseminated to farmers and institutions through the development of extension materials, direct training, and visit programmes for farmers and staff from other key institutions. Project impact was maximised by the use of mass media, including a series of radio programmes, the production of three television documentaries and a series of 12 extension leaflets in Vietnamese used to support training, 9 of which were reprinted with funding from the Central Extension Centre after READ ended. Significant READ successes included the breeding of several indigenous fish species; the establishment of localised fish seed distribution networks of hatcheries and nurseries; and the Vietnam Bank of Agriculture and Rural Development providing credit for fish culture for the first time on the strength of READ trial farmer results. READ moreover facilitated the establishment of a pilot aquaculture extension network at the community level; strengthened links and information flow between key stakeholders; and provided training and support to agencies and institutions (formal and informal) that influence and support the livelihoods of farmers.

DSPIR Framework as Planning and Management Tools for the La Boquita Coastal System, Manzanillo, Mexico

Coastal ecosystems are attractive sites for tourism. In the central Pacific coast of Mexico in the La Boquita coastal system (LBCS), consisting of a beach and a coastal lagoon, the Driver-Pressure-State-Impact-Response (DPSIR) model was implemented for the spatial and temporal analysis of socio environmental indicators, aiming to gather information for decision-making and implementation of management strategies. The spatial occupation (umbrellas and tables) of the beach showed a 50–200% increase during the Easter season relative to the low season, while the area containing restaurants (called “ramadas”) increased by 396% in 15 years, representing pressure on land use for tourism purposes. The density of beach users ranged from moderate to high (<10 m2/user) during the holiday seasons in the tourism area. The Trophic index (TRIX), used as an indicator of trophic status, revealed mesotrophic-to-eutrophic conditions in lagoon water due to the limited water exchange with the adjacent ocean and to DIN and DIP inputs from adjacent tourist areas. The analysis of the environmental legislation showed that law enforcement in the LBCS is poor or nil, with most environmental regulations either ignored or having inadequate enforcement monitoring. This has led to the current state of socio environmental disruption.

Response of macrobenthic communities to changes in water quality in a subtropical, microtidal estuary (Oso Bay, Texas)

The influence of nutrient loading and other anthropogenic stressors is thought to be greater in low inflow, microtidal estuaries, where there is limited water exchange. This 11-month study compared spatial changes in macrofaunal communities adjacent to regions that varied in land cover in Oso Bay, Texas, an estuarine secondary bay with inflow dominated by hypersaline discharge, in addition to discharge from multiple municipal wastewater treatment plants. Macrofauna communities changed in composition with distance away from a wastewater treatment plant in Oso Bay, with the western region of the bay containing different communities than the head and the inlet of the bay. Ostracods were numerically dominant close to the wastewater discharge point. Macrobenthic community composition is most highly correlated with silicate concentrations in the water column. Silicate is negatively correlated with salinity and dissolved oxygen, and positively correlated with nutrients within the bay. Results are relevant for environmental management purposes by demonstrating that point-source discharges can still have ecological effects in hydrologically altered estuaries.

WATER EXCHANGE IN THE ESTUARY OF THE RAZDOLNAYA RIVER (AMUR BAY, JAPAN SEA) IN THE ICE COVERED PERIOD

Environmental conditions in the Razdolnaya/Suifen Estuary and adjacent marine area were monitored from 2008 to 2018, by seasons, including winter observations in January 2014 and January 2018. The river discharge in winter was low: 6 m3 /s (mean annual discharge is 73 m3 /s). The estuary was covered by ice. The cline of salt water at the bottom was traced upstream up to 28 km from the river mouth. The currents in the estuary changed in tidal cycle. Increasing of salinity and temperature (> 2о ) at the bottom was observed in the distance 20–24 km from the river bar (this area was distinguished by relatively thin ice, 20 cm, against 40–70 cm in the rest of estuary). Modeling of the water balance in the estuary showed an additional source of salt water in the internal estuary, beyond the direct exchange with the sea over the river bar, that was presumably the water flow through the aquifer. This groundwater discharge was responsible for supporting of the salted bottom layer and for temperature and salinity increasing in the internal estuary during the ebb phase in conditions of limited water exchange by two-layered estuarine circulation because of ice cover at the river mouth.

HYDROCHEMICAL STUDIES OF THE PARTIZANSKAYA RIVER ESTUARY (NAKHODKA BAY, JAPAN SEA) IN SUMMER SEASON OF LOW WATER DISCHARGE

Chemical water parameters in the Partizanskaya River estuary were measured on July 18–19, 2012 in conditions of low water discharge (20.1 m3 /s). In these conditions, the cline of salt water at the bottom penetrated up to 11 km upstream from the river mouth and the fresh river water passed the estuarine zone of mixing in approximately 2 days. Salt composition of the mixed water in the estuary had conservative dependence on salinity. By dynamical signs, the estuary could be divided into two zones: i) zone of active exchange between the surface freshwater layer and the bottom salted layer on the distance 5.5 km from the river mouth to the first sandy riverbank that the fresh river water passed in 12 hours, and ii) the upper part of the estuary with limited water exchange. The complex of water environments in the estuary, as good water transparency, strong stratification, and high concentrations of terrestrial nutrients, was favorable for phytoplankton blooming, so the chlorophyll concentration in the estuarine waters exceeded 40 μg/L. Destruction of autochthonous organic matter caused anomalies in distribution of carbonate and nutrient parameters and was accompanied by hypoxia in the bottom layer with the dissolved oxygen content lowering to 61 μM/kg.

Biological factor controlling methane production in surface sediment in the Polish part of the Vistula Lagoon

Due to the limited water exchange, lagoons are particularly prone to eutrophication. The consumption of oxygen in this process, coupled with simultaneous enrichment of bottom sediments with organic matter, reinforces the occurrence of anaerobic conditions and methanogenic growth. Methanogenic archaea activities cause depolymerization of organic compounds accumulated in sediments. As a result of such ecosystem transformation, methane might be produced and emitted from this basin. Chemical studies conducted in 2010 were focused on methane content in the surface bottom sediments in the Polish part of the Vistula Lagoon. The results showed that the highest methane concentration occurs in the southwestern part of this basin (6.45 mmol dm

Carbon-isotope signatures of Albian to Cenomanian (Cretaceous) shelf carbonates of the Natih Formation, Sultanate of Oman

ABSTRACT The δ13C values of Albian to Cenomanian shallow-marine carbonate sequences of the Natih Formation have been collected from subsurface cores of a key location in Oman. The 450-m-thick stack of shelf carbonates is without significant gaps in deposition. The δ13C data range between 1‰ and 6‰, more-or-less tracking the evolution over time of δ13C in seawater established elsewhere in time-equivalent pelagic carbonate sequences. Anchored by biostratigraphy the isotope profile suggests several additional time correlations. It thus provides significantly enhanced stratigraphic resolution and a key section for regional correlations. In particular, the onset of Natih deposition (Natih F and G members) coincides with the Albian/Cenomanian boundary event, thus placing the base Natih into the Albian. The Natih C and D members were deposited mainly during the Mid-Cenomanian oceanic anoxic event, while the carbon-isotopes signature of the Natih A Member, which is at this locality incomplete due to erosion, documents the onset of the Cenomanian/Turonian boundary event (OAE2). This indicates a latest Cenomanian, possibly Early Turonian age for the top Natih at this subsurface location and suggests an Early Turonian age for the more complete Natih section exposed in the nearby Oman Mountains sections. Both organic-rich intervals of the Natih Formation (Natih E4b and B2) do not correlate with global Oceanic Anoxic Events indicating a rather local setting for source-rock deposition. This is further supported by an isotopic anomaly associated with the organic-rich Natih B. The anomaly is likely related to near-seabed diagenesis or a temporary limited water exchange of the intra-shelf basin with the open ocean and the incorporation of recycled carbon from oxidized organic matter into the water column and the inorganic carbon pool. The subsurface carbon-isotope profile correlates well with those from nearby outcrop and other subsurface sections adding further confidence that primary signatures are preserved and can be used for correlations. As in other Early Cretaceous shelf sequences of the Arabian Plate oxygen isotopes are lighter than expected for calcite deposited in equilibrium with Cretaceous seawater indicating most likely whole-scale recrystallization and stabilization during shallow burial at slightly elevated temperatures.