Seasonal variability of fine-sediment in the Tamar estuary

Measurements describing the intratidal, spring-neap and seasonal variations of fine, cohesive, suspended particulate matter (SPM) concentrations at two sites (Calstock and Halton Quay) within the upper reaches of the Tamar Estuary, UK, are presented. The data were obtained using two, near-bed instrument packages. Correlations of daily-averaged SPM concentrations and fluxes with both runoff and tidal range during the separate deployments often showed a significant dependence on these variables. Where statistically significant, increasing tidal range led to enhanced SPM levels because of resuspension of bed sediments.

Particle Dynamics Particulate Carbon And The Oxygen Minimum In An Estuary

Profiles of suspended particulate load and its organic and inorganic carbon contents as well as salinity, dissolved oxygen, ammonia and divalent manganese have been recorded throughout the mixing region of the Tamar Estuary,Southwest England, in late summer when there was pronounced net oxygen consumption. The results indicate that trapping of particulate organic detritus (of both riverine and marine origins) within the high turbidity zone contributes to the localisation and buffering of the seasonal oxygen demand exerted within the low salinity region of the estuary.

Nutrient Distributions In An Estuary - Evidence Of Chemical Precipitation Of Dissolved Silicate And Phosphate

Continuous autoanalytical recordings of the axial distributions of dissolved nitrate, silicate and phosphate in the influent freshwater and saline waters of the Tamar Estuary, south-west England have been obtained. Short-term variability in the distributions was assessed by repetitive profiling at approximately 3-h intervals on a single day and seasonal comparisons were obtained from ten surveys carried out between June 1977 and August 1978. Whereas nitrate is always essentially conserved throughout the upper estuary, the silicate- and phosphate-salinity relationships consistently indicate a non-biological removal of these nutrients within the low (0–10%) salinity range. Attempts to quantify precisely the degree of removal and to correlate this with changes in environmental properties (pH, turbidity, chlorophyll fluorescence, salinity, freshwater composition) were mainly inconclusive due to short-term fluctuations in the riverine concentrations of silicate and phosphate advected into the reactive region and to the rapid changes in turbidity brought about by tidally-induced resuspension and deposition of bottom sediment.

The prediction of nutrients into estuaries and their subsequent behaviour: application to the Tamar and comparison with the Tweed, U.K.

Some of the techniques used to model nitrogen (N) and phosphorus (P) discharges from a terrestrial catchment to an estuary are discussed and applied to the River Tamar and Tamar Estuary system in Southwest England, U.K. Data are presented for dissolved inorganic nutrient concentrations in the Tamar Estuary and compared with those from the contrasting, low turbidity and rapidly flushed Tweed Estuary in Northeast England. In the Tamar catchment, simulations showed that effluent nitrate loads for typical freshwater flows contributed less than 1% of the total N load. The effect of effluent inputs on ammonium loads was more significant (∼10%). Cattle, sheep and permanent grassland dominated the N catchment export, with diffuse-source N export greatly dominating that due to point sources. Cattle, sheep, permanent grassland and cereal crops generated the greatest rates of diffuse-source P export. This reflected the higher rates of P fertiliser applications to arable land and the susceptibility of bare, arable land to P export in wetter winter months. N and P export to the Tamar Estuary from human sewage was insignificant. Non-conservative behaviour of phosphate was particularly marked in the Tamar Estuary. Silicate concentrations were slightly less than conservative levels, whereas nitrate was essentially conservative. The coastal sea acted as a sink for these terrestrially derived nutrients. A pronounced sag in dissolved oxygen that was associated with strong nitrite and ammonium peaks occurred in the turbidity maximum region of the Tamar Estuary. Nutrient behaviour within the Tweed was very different. The low turbidity and rapid flushing ensured that nutrients there were essentially conservative, so that flushing of nutrients to the coastal zone from the river occurred with little estuarine modification.

Validation and in situ application of an automated dissolved nickel monitor for estuarine studies

The validation of a fully automated dissolved Ni monitor for in situ estuarine studies is presented, based on adsorptive cathodic stripping voltammetry (AdCSV). Dissolved Ni concentrations were determined following on-line filtration and UV digestion, and addition of an AdCSV ligand (dimethyl glyoxime) and pH buffer (N-2-hydroxyethylpiperazine-N′-2-ethanesulphonic acid). The technique is capable of up to six fully quantified Ni measurements per hour. The automated in situ methodology was applied successfully during two surveys on the Tamar estuary (south west Britain). The strongly varying sample matrix encountered in the estuarine system did not present analytical interferences, and each sample was quantified using internal standard additions. Up to 37 Ni measurements were performed during each survey, which involved 13 h of continuous sampling and analysis. The high resolution data from the winter and summer tidal cycle studies allowed a thorough interpretation of the biogeochemical processes in the studied estuarine system.

Primary Production In An Estuarine Environment - Comparison Of Insitu And Simulated Insitu C-14 Techniques

A simulated in situ incubation box has been compared with in situ exposure for 14C production measurements in an estuarine environment. Measurements were made over the course of 14 months, mainly in the Tamar estuary; production rates ranged from less than 1 mg C m−2h−1 to 350 mg C m−2h−1 and there was no significant difference between results from the two methods. In the estuarine waters investigated, the simulated in situ incubator with neutral density filters, used with a Secchi disc to determine sampling depths, gives a satisfactory estimate of in situ primary production.

Protohydra leuckarti near Plymouth

A new location for Protohydra leuckarti is reported near Plymouth at Millbrook Lake (Tamar Estuary). To place this finding in context, notes follow on a familiar habitat of this species in the White Sea, and on the general ecology and distribution Of Protohydra and its enigmatic phylogeny.