Cumberland Basin Research Articles

The Lapstone structural complex, New South Wales

The Lapstone Structural Complex forms the most prominent topographic feature in the Sydney region. The complex consists of a number of related folds and faults, trending generally north‐south, which together form a large south‐plunging structure between Kurrajong Heights and Lapstone. The east‐facing escarpment of the Blue Mountains, formerly called the Lapstone Monocline, varies in its character, being sometimes a single monocline, sometimes a double monocline and sometimes a normal or high‐angle reverse fault. Faulting west of Kurrajong and at Glenbrook is part of a series of overlapping en echelon faults, west‐side down, and sometimes overturned, rather than a single fault. This fault system forms the west side of the complex. Significant minor structures associated with major features include thrusts, minor folds, joint systems, tectonic breccias, sedimentary injections and igneous dykes. Many of the minor structures show a marked parallelism with the major structures. The main period of deformation forming the complex is believed to have taken place in the Early Tertiary, but the overall structure has a long and complex history. Field evidence suggests that sinistral strike‐slip faulting played a part in the deformation, particularly of the near‐surface rocks. Basement block faulting was also significant, producing the Cumberland Basin and associated structures when the main Lapstone structures were formed. Basement structural control is believed to consist of the northerly extension of the western edge of the Eden‐Comerong‐Yalwal Rift intersected by elements of the east‐trending Lachlan Lineament.

Suspended sediment transport processes in Cumberland Basin, Bay of Fundy

Cumberland Basin, located at the head of Chignecto Bay, Bay of Fundy, exhibits a seaward (exponential) decreasing, time‐dependent, surface sediment concentration. There is a strong correlation between suspended sediment concentration and longitudinal concentration gradient. A similar correlation was found in Shepody Bay, Chignecto Bay, and Minas Basin, suggesting that an equilibrium condition exists between the two variables. Total suspended mass in Cumberland Basin was constant over 2 years of observation (1011 g) despite changes in sediment concentration and concentration gradient. Temporal controls on suspended sediment concentration are river influx, ice melting, dispersion, settling on the intertidal mud flats, and water mass exchange at the mouth of the basin. This exchange is due to cross‐channel velocity variations; exchanges due to tidal current asymmetry and settling lag are small. A simple box model was developed to study the temporal variation of total suspended sediment in the basin. The results show that the water mass exchange at the basin mouth varies with time and is the dominant factor controlling suspended mass due to efficient dampening of temporal fluctuations in suspended mass.

Sediment-Water Exchange of Dissolved Nutrients at an Intertidal Site in the Upper Reaches of the Bay of Fundy

Concentrations of dissolved nitrate, silicate, and phosphate in water flooding intertidal sediments at Pecks Cove and along the axis of Cumberland Basin, Bay of Fundy were measured throughout the year. Exchanges of dissolved nutrients between intertidal sediments and overlying water were measured by enclosing water in chambers over undisturbed sediment. Nitrate concentrations in the water usually decreased during incubations while silicate was released by sediments during summer and consumed during fall. Particles which settled in sediment traps exposed during periods of high tide were stirred in filtered seawater to measure nutrient exchange. The flux of nutrients between the intertidal sediments and settled particles and seawater was estimated from incubation experiments and the observed nitrogen content in surface sediments and suspended particulate material. There was a net import of dissolved nitrate and silicate into Cumberland Basin from Chignecto Bay during early summer, at all other times there was a net export. Despite the low primary productivity and rigorous physical environment, biological activity has a measurable impact on dissolved nutrient concentrations in the waters of Cumberland Basin.

Ecological evaluation of the Cumberland Basin [Bay of Fundy] ecosystem model : Gordon, D.C. Jr., P.D. Keizer, Peter Schwinghamer and G.R. Daborn, 1987. Continent. Shelf Res., 7(11–12):1477–1482

Ecological evaluation of the Cumberland Basin [Bay of Fundy] ecosystem model : Gordon, D.C. Jr., P.D. Keizer, Peter Schwinghamer and G.R. Daborn, 1987. Continent. Shelf Res., 7(11–12):1477–1482

Ecological evaluation of the Cumberland Basin ecosystem model

A holistic ecosystem simulation model has been developed for the Cumberland Basin and upper Chignecto Bay, a turbid macrotidal estuary at the head of the Bay of Fundy. This one-dimensional deterministic model has three compartments, three boundaries and three interacting submodels (physical, pelagic and benthic). Twenty-eight biological state variables represent broad functional groups of organisms and non-living organic carbon pools. All major components of the estuarine ecosystem are included. At the present stage of development, individual pelagic state variables give reasonable annual simulations which are in general agreement with available calibration data. Major problems remain with some benthic state variables, especially the subtidal ones about which little is known. In aggregate, the model performs well and output at the ecosystem level agrees with field observations. In the Cumberland Basin water column, annual community respiration exceeds phytoplankton net production (1–3 g C m −3) by a factor of 2–5 suggesting the importance of carbon imported from surrounding saltmarshes and the seaward boundary. Annual community respiration and microalgal net production (28 g C m −2) on the other hand are closely balanced in intertidal sediments. Respiration in subtidal sediments is entirely dependent upon sedimented carbon. The model supports the hypothesis that the Cumberland Basin is a heterotrophic ecosystem with low primary production which requires imported organic carbon to support the production and respiration of higher trophic levels.

Identification of Microdetritus Derived from Spartina and Its Occurrence in the Water Column and Intertidal Sediments of Cumberland Basin, Bay of Fundy

A cellulose-specific staining procedure employing Herzberg’s chlor-zinc-iodide solution was developed to aid in the identification of microdetritus derived fromSpartina alterniflora and tested on samples of suspended and sedimented particulate matter collected in the Cumberland Basin at the head of the Bay of Fundy. Not all of the particles reacting positively to the stain could have been identified as originating fromSpartina on the basis of morphology alone, and the stain improved speed and confidence in identification even when particles could be identified morphologically.Spartina dominated particles greater than 100 μm while most of the smaller particles were amorphous aggregates of uncertain origin. In April 1985, at the start of the salt-marsh growing season, the average concentration of suspended microdetritus derived fromSpartina in Cumberland Basin surface water was 129 mg C m−3 or 0.3–2.7% of the particulate organic carbon. The average concentration in intertidal sediments was 0.036 mg C g−1 or 0.2–0.9% of the sediment organic carbon. Summing all reservoirs in the sediment (to a depth of 1 cm) and water column, the total amount of detritus originating fromSpartina in Cumberland Basin is 10–24% of the estimated annual net primary production of low marshS. alterniflora.

Population dynamics and nutrition of Corophium volutator (Pallas) in the Cumberland Basin (Bay of Fundy)

Corophium volutator (Pallas), a tube-dwelling amphipod, is the dominant macro-invertebrate in intertidal mudflats of the Bay of Fundy. Abundance and biomass were followed at two sites from May to October. In spring, the population consisted primarily of a small overwintering generation. The release of young resulted in peak densities of up to 15000 individuals·m −2 in late June/early July. Numbers and biomass then declined drastically, in part because of heavy predation by migrant shorebirds. Their departure allowed a partial recovery of the C. volutator population. C. volutator biomass or density showed either no or weak correlation with organic, protein or chlorophyll content of the sediment. Organic particles amounted to <0.1% of mud dry wt, suggesting that over 90% of the organic content of mud is in solution, or concentrated at particle/water interfaces. Both Spartina and diatoms contributed at most 1% to the gut content of Corophium. Bacterial numbers declined from anterior to posterior part of the gut by ≈60%. The maximum contribution of identifiable food items to the nutrition of Corophium has been estimated at 46.5% ( Spartina, 3.8%; diatoms, 11.4%; bacteria, 31.3%); the average is below 4%. Immunofluorescence and a complement fixation assay were used to identify gut contents further but neither was completely satisfactory. There is some indication, however, that in addition to organic matter associated with mud, seaweed-derived material may play a minor role in the nutrition of Corophium.

Adventures in holistic ecosystem modelling: the cumberland basin ecosystem model

A holistic ecosystem model has been developed for the Cumberland Basin, a turbid macrotidal estuary at the head of Canada's Bay of Fundy. The model was constructed as a group exercise involving several dozen scientists. Philosophy of approach and methods were patterned after the BOEDE Ems-Dollard modelling project. The model is one-dimensional, has 3 compartments and 3 boundaries, and is composed of 3 separate submodels (physical, pelagic and benthic). The 28 biological state variables cover the complete estuarine ecosystem and represent broad functional groups of organisms based on trophic relationships. Although still under development and not yet validated, the model has been verified and has reached the stage where most state variables provide reasonable output. The modelling process has stimulated interdisciplinary discussion, identified important data gaps and produced a quantitative tool which can be used to examine ecological hypotheses and determine critical environmental processes. As a result, Canadian scientists have a much better understanding of the Cumberland Basin ecosystem and are better able to provide competent advice on environmental management.

Fidelity of American Shad, Alosa sapidissima (Gupeidae), to its River of Previous Spawning

Of 5074 adult American shad, Alosa spidissima, tagged in the Annapolis River, Nova Scotia, during the 1981 and 1982 spawning runs, 292 (5.8%) were recaptured, 180 in the river during the same year, 56 in the river in subsequent years, 53 at distant marine sites, and 1 in another Nova Scotia river. Recovery from 6124 adult shad tagged in a marine environment (Cumberland Basin, Bay of Fundy) was similar (395 recaptures, 6.5%) but distribution was markedly different. Thirty-five were taken in the Basin during the same year, but only 7 in subsequent years. Conversely, 139 were recaptured at distant marine sites, and 214 in rivers from the St. Lawrence River, Quebec, to the St. John's River, Florida. Assuming equal probabilities for recapture within this species' geographical range, Annapolis River freshwater recaptures were specific for the Annapolis River but Cumberland freshwater recaptures were nonspecific. Except for two returns, possible strays, fidelity to the Annapolis was 97%.

Nutrient dynamics in cumberland basin - chignecto bay, a turbid macrotidal estuary in the bay of fundy, canada

The Bay of Fundy is a turbid, high-energy, macrotidal estuary on Canada's east coast. An extensive ecological study of this area has been conducted over the past 5 years. The concentration of nutrients was measured in numerous compartments of this ecosystem on different scales of time and space. While nutrient concentrations in the water column never approached limiting values, concentrations were a complex function of numerous physical and environmental factors. The effects of high concentrations of suspended sediments and the high energy input from the large tidal range on the dynamics of nutrients in this estuary are discussed in detail in an attempt to evaluate sources and sinks of nutrients in the estuary. Due to lack of information on residual water fluxes, estimations of the magnitude and direction of nutrient fluxes in the estuary are only qualitative.

Population dynamics and production of Macoma balthica in Cumberland basin and Shepody Bay, Bay of Fundy

The distribution of Macoma balthica in Cumberland Basin and Shepody Bay is very patchy and the zone of greatest abundance consistently occurs near the upper mudflat boundary where exposure time is greatest. The primary factors influencing distribution appear to be food availability, sediment stability and mortality. Sediment properties appear to play a minor role in this environment. Ice scour, sediment instability, predation and possibly high temperatures contribute to the high specific mortality rate (−0.5 y −1) resulting in a maximum age of 5 years. Growth and reproductive cycles of Macoma are the same as observed elsewhere except that lower winter temperatures delay growth to a few months between May and August. Annual Macoma production, averaged over several entire mudflats, is 0.5 and 3.9 g flesh dry weight m −2 for Cumberland Basin and Shepody Bay respectively, or 10 and 50% of the estimated total macrofauna production.

Population carbon budgets and the importance of the amphipod corophium volutator in the carbon transfer on a cumberland basin mudflat, upper bay of fundy, Canada

The importance of Corophium volutator in the carbon flux between microalgal primary producers and other trophic levels was evaluated from population carbon budgets. In all but 4 of 39 population carbon budgets the estimated consumption was sufficient to meet the demands of production and respiration combined. A carbon budget constructed for the period from May to September 1979 revealed that Corophium production accounted for 40% of the consumption, respiration for 25% and the remainder by difference was attributed to faecal waste. Consumption was equivalent to 27% of the “net” epibenthic microalgal primary production over the same time period. Marked temporal changes in Corophium abundance appear to influence rates of benthic microalgal primary production during summer. Concurrently, an approximate 20-fold increase in Corophium biomass provides a significant food resource for birds and fishes. This implies that Corophium occupies a key link in processes of carbon flux on mudflats in the upper reaches of the Bay of Fundy.

Occurrence of Spartina Macrodetritus in Bay of Fundy Waters

Suspended macrodetritus (>600 μm) from extensiveSpartina alterniflora marshes is widespread in the Cumberland Basin region of the macrotidal upper Bay of Fundy. The average concentration is about 5 mg C per m3 and most is found in the lower two-thirds of the water column. The total amount in the Basin at high tide is approximately 8 metric tonnes of organic carbon which is less than 1% of the annual net aerial primary production of the fringingS. alterniflora marshes. The high visibility ofSpartina detritus in Cumberland Basin is caused by the extreme tides (average tidal range about 11 m) which export marsh vegetation and distribute it widely about the estuary, and by the pronounced turbidity which has been shown to limit phytoplankton growth.

Observations on the ecological importance of salt marshes in the Cumberland Basin, a macrotidal estuary in the Bay of Fundy

The Cumberland Basin, a 118 km 2 estuary at the head of the Bay of Fundy which has an average tidal range of about 11m, contains large tracts of salt marsh (15% of the area below highest high water). Low marsh (below about 0·9 m above mean high water) is composed almost exclusively of Spartina alterniflora while the vegetation on high marsh is more diverse but dominated by Spartina patens. Because of its higher elevation, high marsh is flooded infrequently for short periods by only extreme high tides. Low marsh is inundated much more frequently by water as much as 4m deep for periods as long as 4 h per tide. Temporal variability in the occurrence of extreme tides influences the flooding frequency of high marsh for any given month and year. Using a modification of Smalley's method, the mean annual net aerial primary production (NAPP) of low and high marsh is estimated to be 272 and 172 g C m −2, respectively. Vegetation turnover times average 1·0 and 2·0 y for low and high marsh, respectively. Because of abundant tidal energy, much of the low marsh production appears to be exported and distributed widely about the estuary. Since high levels of turbidity suppress phytoplankton production, salt marshes produce approximately half of the carbon fixed photosynthetically in the Cumberland Basin. It is concluded that salt marshes play a major ecological role in the Cumberland Basin.

Primary Production and Respiration in Pelagic and Benthic Communities at Two Intertidal Sites in the Upper Bay of Fundy

Primary production by microalgae on intertidal sediments during ebb tide at two sites in Cumberland and Minas Basin, Bay of Fundy, amounted to 47–83 g C∙m−2∙yr−1 Phytoplankton production measured during flood tide over intertidal sediments in Cumberland Basin varied from 4–10 g C∙m−2∙yr−1 with respiration in the water column between 6 and 12 g∙C∙m−2∙yr−1 depending on concentrations of suspended matter. Respiration by undisturbed sediments (47–62 g C∙m−2∙yr−1) was measured at both locations to estimate aerobic metabolic consumption of organic matter.Maximum rates of benthic primary production occurred during early and late summer at both locations but Values at the Cumberland Basin sites were two to three times greater than those observed in Minas Basin; Chlorophyll a in surface sediments was also lower at the stations in Minas Basin where coarser grained deposits reflect extensive sediment transport. Annual benthic respiration at the two stations in Cumberland Basin, however, was only slightly greater than that at four stations in Minas Basin. Spartina marshes, phytoplankton, and benthic microalgae may provide supplies of organic matter for aerobic consumption in these intertidal sediments which are more similar than are measures of benthic primary production.Key words: benthic microalgae, primary production, intertidal community metabolism, Bay of Fundy

Stable Carbon Isotope Studies on the Pecks Cove Mudflat Ecosystem in the Cumberland Basin, Bay of Fundy

Ratios of stable carbon isotopes (δ 13C) have been measured in components of an intertidal mudflat ecosystem located near the head of the Bay of Fundy. Special attention was given to the isolation and analysis of carbon source materials including phytoplankton, benthic algae, marsh grass (Spartina alterniflora), size-fractionated detritus, and "mineral" sediment. Bulk sediment and suspended matter were also analyzed. For most of the year the two major primary producers, Spartina and benthic diatoms (dominated by Gyrosigma spp.), had similar δ 13C values (−13 to −14‰). Some Spartina detritus, presumably "fresh" material, also had similar δ 13C values. It was therefore imposible to estimate the relative importance of carbon from these sources to the nutrition of consumer organisms. Zooplankton, benthic-feeding fish, and benthic fauna had δ 13C values mostly in the range of −12 to −15‰, suggesting that live Spartina, "fresh" detritus, and benthic diatoms could be major carbon sources. Phytoplankton and other isotopically light carbon sources including "aged" detritus, bulk and "mineral" sediment, do not appear to be major carbon sources for mudflat organisms. We found Spartina detritus to be abundant both in sediments and suspended matter outside the salt marshes, but the δ 13C values of most of the detritus were much lighter (−17 to −20‰) than those of live Spartina. The mechanism of this isotopic alteration is not known and we were not able to demonstrate it clearly in laboratory experiments. Although the δ 13C method has helped to assess the relative importance of some isotopically distinct carbon sources, we were unable to detect any 13C enrichment in various trophic levels of mudflat organisms and benthic-feeding fish.Key words: stable carbon isotope ratio, detritus, decomposition, mudflat ecosystem, Pecks Cove, Bay of Fundy

Effect of Turbidity on the Temporal and Spatial Utilization of the Inner Bay of Fundy by American Shad (Alosa sapidissima) (Pisces: Clupeidae) and its Relationship to Local Fisheries

Since 1750, a unique, directed fishery for American shad (Alosa sapidissima) has existed in shallow, turbid, mega-tidal embayments of the inner Bay of Fundy during summer and fall. Tagging experiments indicated that migrating shad consisting of intermixed, river populations from the entire Atlantic coast of North America occur there between June and October. Shad migration was counterclockwise around the Bay following the residual current structure. Presence and duration of the shad run in Cumberland Basin was a result of interaction between migration timing, turbidity, and temperature. Mean daytime swimming depth was related to tidal phase and turbidity. High turbidity (Secchi [Formula: see text]) of the mega-tidal embayments apparently extends the preference zone for light intensity of ocean-feeding shad into surface waters (2–10 m), making them accessible to the local fishery.Key words: drift gillnets, shad migration, light intensity preference, swimming depth, mega-tidal, eastern Canada

Seasonal Variation in Weight-Specific Growth Rates, Feeding Rates, and Growth Efficiencies in Microgadus tomcod

Among Microgadus tomcod from Cumberland Basin, Bay of Fundy, exponents of the weight–length relationship (liver, gonads removed) ranged from 2.74 in April, after spawning, to 3.47 in September, after summer feeding. This implies that growth rate per unit of weight is seasonally higher in larger fish, although this diminishes on an annual basis after 2 yr in these short-lived (&lt; 4 yr) fish. In feeding experiments larger fish after spawning increased feeding (weight-specific ration declined with weight in September, not in April-May) and grew faster, using proportionately more food for growth (growth efficiency not correlated with weight in September, positively so in April–May).

Dynamics and Environmental Effects of Ice in the Cumberland Basin of the Bay of Fundy

Ice occurs in the upper reaches of the Bay of Fundy from December to April and conditions are influenced by the macrotides characteristic of the area. Drift ice forms on the seawater surface and because of almost constant movement in tidal currents is composed of small, rounded pieces. Shorefast ice develops from the stranding of drift ice between the neap and spring high water levels. Drift ice can also strand during ebb tide on intertidal salt marshes and mudflats which together comprise two-thirds of the Cumberland Basin area. Intertidal sediments can freeze to form a frozen crust, and sheet ice can form where salinity and tidal energy are low. Shorefast ice can significantly reduce the cross-sectional area of tidal rivers and encourage flooding. Stranded drift ice can import sediment and export plant debris from salt marshes. Mudflats are heavily scoured by ice all winter which causes erosion and mortality of benthic organisms. Construction of a tidal power project would change ice properties considerably.

A preliminary comparison of two turbid coastal ecosystems: The Dollard (Netherlands-FRG) and the Cumberland Basin (Canada)

Extensive ecological studies are currently being conducted in the Ems-Dollard estuary and the upper reaches of the Bay of Fundy. The purpose, approach, results, synthesis and application of each project are compared in a preliminary fashion, with emphasis upon the Dollard and the Cumberland Basin. Both regions are turbid, shallow water environments with extensive intertidal areas. Although important differences do exist, for example greater tidal energy and suspended sediment concentrations in Cumberland Basin and pronounced import of allochthonous organic carbon in the Dollard, similar organisms and ecological processes dominate both estuaries and secondary production does not appear to be significantly different. High levels of stress in both environments favor the development of small and rapidly growing organisms. Comparison exercises such as this are extremely valuable for judging progress, evaluating results and stimulating new ideas.