Charles T. Schafer

A multidisciplinary approach to evaluating impacts of shellfish aquaculture on benthic communities

The impact of suspended mussel culture (Mytilus edulis, M. trossulus) on the benthos of a small Nova Scotia cove (7 m depth) was assessed using meehods involving both benthic metabolism and community structure. Due to deposition of mussel feces and pseudofeces, sedimentation rate was higher under the mussel culture lines than at an adjacent reference site of similar sediment texture. Porewater profiles of sediment sulfate and sulfide indicated greater anaerobic metabolism at the mussel site than at the reference site, but sulfide was absent from the upper centimeters of sediments under the mussels. Seasonal measures of sediment oxygen demand showed little change between sites, but maximum rates of ammonium release at the mussel site were twice the highest rates measured at the reference site. Abundance of benthic macrofauna was higher at the reference site, but biomass was generally lower. Biomass at the mussel site was dominated by molluscs (Ilyanassa spp. andNucula tenuisulcata), that were attracted to mussels fallen from the culture and/or enriched organic matter due to biodeposition. Species diversity was lower at the reference site due to the dominance of the polychaeteNephtys neotena. Abundance-biomass comparisons (ABC method) of faunal analysis did not indicate any impact of biodeposition at this site: however, disturbance did not result in a typical assemblage of small opportunistic species anticipated with this method. Cluster analysis of macrofauna usually provided a clear separation between the sites. Since the contruction of a causeway (1968), foraminifera species composition showed a temporal response to temperature changes in the cove by shifting toward calcareous species, but assemblages downcore showed little or no relationship to aquaculture impacts. Although there is a shift toward anaerobic metabolism at the mussel lines, the impact of mussels falling to the sediments was more noticeable in benthic community structure than was any impact due to organic sedimentation or hypoxia. In general the impact of aquaculture on the benthos appeared to be minor. Furtyher assesment of these consequences may mandate both taxonomic and energetic approaches to impact assessment.

Evidence for an earthquake-triggered basin collapse in Saguenay Fjord, Canada

Abstract On February 5, 1663, perhaps the largest earthquake ever witnessed in eastern North America struck the Saguenay Fjord basin with such force that landslides and submarine slides were triggered over a wide region. Over 3 km 3 of clayey Holocene sediments collapsed from the margins of the fjord, resulting in amalgamated debris flow and slide deposits that covered much of the basin floor. These deposits reached thicknesses of up to 100 m, and extended over an area of 100 km 2 . The ambient seafloor was compressed under the impact and load of these debris masses, and/or liquefied under the cyclic stress of the seismic wave. A 0.2 km 3 landslide also occurred at this time, blocking the Saguenay River and possibly facilitating an extra large spring freshet (discharge). Biotracers (planktonic and benthic foraminifera, arcellaceans, pollen and wood), in conjuction with mass physical properties of sediment cores and high-resolution seismic and sidescan profiler data, have been used to identify local and distal sediment sources, including their original water depth of deposition, and their subsequent mode of mass gravitational transport. The landslide material was eroded by the river, and super-elevated sediment concentrations are considered responsible for a long-lasting (28 days) turbidity current that entered the Saguenay Fjord depositing a single 0.3 km 3 turbidite. The 2 to 10 m thick turbidite is considered to have been self-igniting having eroded into the surface of the collapsed basin debris. Paleo-hydraulic calculations suggest that this turbid flow averaged 0.45 m/s and reached a flow thickness of 30 m.

Relationship of Foraminifera and thecamoebian distributions to sediments contaminated by pulp mill effluent: Saguenay Fiord, Quebec, Canada

Gravity cores and grab samples collected in the Saguenay Fiord between 1976 and 1988 contain the record of a 20th century benthic marine environment contaminated primarily by organic matter discharges from several local pulp and paper mills.Spiroplectammina biformis is the dominant arenaceous species. Its living percent abundance decreases between 1982 and 1988 as a consequence of the apparent recolonization of the upper reaches of the fiord by several arenaceous taxa, the most important beingTextularia earlandi. Cassidulina reniforme, the dominant living calcareous species, shows about a three fold increase in relative abundance over the six year interval. Grab sample observations also suggest a recolonization of some formerly barren benthic environments near the head of the fiord by foraminiferal species between 1982 and 1988. This recolonization may reflect the combined effect of government regulations imposed on local industrial polluters in the early 1970s and the capping of a large area of contaminated sediment by a layer of clay that was transported to the basin at the head of the fiord as the result of a catastrophic landslide in 1971. X-radiographs of core sections from a basin at the head of the fiord show sharp laminations that reflect both the absence of bioturbators and the seasonal variation of fluvial depositional processes. Organic waste deposition from pulp and paper mill outfalls first increased around 1910 and shows a first order inverse relationship to benthonic foraminiferal assemblage diversity. The presence of only allochthonous thecamoebian and reworked planktonic Foraminifera tests in many benthonic Foraminifera-barren core intervals supports the idea that common indigenous estuarine species such asSpiroplectammina biformis were excluded from these areas at certain times as a consequence of pollution “stress” rather than having been removed from the sediment record as a result of post-depositional diagenetic effects. However, future studies of estuarine pollution history based on proxy foraminiferal data from cores must give greater emphasis to distinguishing ecological stress responses from diagenetic process (i.e. test dissolution effects) since both mechanisms can be reflected in the proxy pollution “signal” in a similar way.

Recent sedimentation events at the head of Saguenay Fjord, Canada

Unbioturbated marine sediments containing a record of high river discharge events occur at the head ofSaguenay Fjord, near Saint Fulgence, eastern Canada. Preservation of allochthonous benthonic foraminifera, recognition of occasional rapid sedimentation events associated with the spring runoff of the Saguenay River, and the unmixed character of the sediment can be used in conjunction with several dating techniques to obtain a temporal resolution of paleoriverine events on a time scale of months to years.The geologic and geochemical record of the upper 150 cm of sediment reflects (1) the anoxic character of the benthic environment, resulting from the high flux of terrigeneous material to the bottom; (2) the transport and deposition of landslide-derived sediment into the head of the fjord over several years; (3) an indication of the nature and timing of dissolution processes that have altered or totally eliminated the allochthonous calcareous microfossil assemblage from the recycled sediment; and (4) a cyclic depositional pattern that may be useful in reconstructing pateoclimatologic trends that have influenced annual river discharge of this drainage system over the past millennium.

A 20th-century record of climatologically modulated sediment accumulation rates in a Canadian Fjord

Abstract The geochronology of a gravity core collected from an anoxic, high sedimentation rate (>2.5 cm/yr) setting near the head of the Saguenay Fjord in Quebec has been established for the period 1900–1979 to a resolution of better than 1 yr using a constant flux 21 Pb model. Interannual variations of the sedimentation rate of between 28 and 50% are caused by rapid inputs of coarse silt and fine sand during spring freshet events. A significant correlation between sand percentage and sediment accumulation rate reflects the increase in stream competence during the spring freshet; the sand percentage parameter can be used in conjunction with sediment size parameters to estimate temporal variations in river discharge intensity. Between 1914 and 1979 sediment accumulation rates were about 60% higher during the spring and summer compared to fall and winter seasons. Both the magnitude of the Saguenay River spring discharge and the quantity of precipitation stored as snow decrease through the 20th century suggesting that the freshet intensity was governed largely by natural rather than anthropogenic (e.g., dam construction) factors. A direct correlation between sand flux, peak river discharge, and a snow storage parameter provides a link between sediment texture and climate. Detailed analyses of the grain-size distributions for dated core intervals offer a method for the reconstruction of a proxy record of paleodischarge for the Saguenay River spring freshets.

Significance of natural and anthropogenic sediment inputs to the saguenay Fjord, Quebec

Abstract One-centimeter interval Pb-210 dating and 4-cm interval size analysis was carried out on a sediment core collected in a prodelta depositional environment near the head of the Saguenay Fjord. Results show a direct relationship between modal diameter of the sand fraction and annual maximum mean monthly river discharge events that are usually associated with the spring freshet. Indirect evidence of sediment flux to the head of the fjord includes a series of sand waves that are developed on a prograding submarine delta at the mouth of the Saguenay River. Clay-pellet zones observed in a gravity core are related to catastrophic events such as the 1971 St. Jean Vianney landslide, or to anthropogenic activities associated with the construction of dams and powerhouses at upriver locations. A subtle change in the slope of a graph relating cumulative annual mean river discharge and sediment accumulation for the 1950–1970 interval is in agreement with the timing of dam construction on the lower reaches of the Saguenay River system.

Evidence of the Occurrence and Magnitude of Terrestrial Landslides in Recent Saguenay Fjord Sediments

The 1971 St. Jean Vianney landslide resulted in the deposition of a distinctive grey-coloured layer of late glacial to early Holocene-age Laflamme Sea clay throughout the upper arm of the Saguenay Fjord. An older comparatively ubiquitous clay layer observed in gravity cores collected from the upper half of the fjord appears to be associated with an exceptionally large 17th century landslide of Laflamme Sea clay and littoral sand deposits that also occurred near St. Jean Vianney. The ancient slide is believed to have been triggered by a major earthquake that occurred in the Saguenay region on February 5, 1663. A cohesive debris flow underlies a sandy clay layer of presumed 1663 slide-related sediments. The debris flow is attributed to local slumping of terrestrial and submarine deposits of Laflamme Sea clay, and of Holocene estuarine sediments, as a result of the initial magnitude 7 earthquake shock. The sandy clay layer of 1663(?) slide sediment appears to have been deposited as a cohesionless mass flow. The flow was probably initiated by the failure of the Saguenay River delta foreslope on which large volumes of reworked landslide sediments would have been deposited by the spring freshet of 1663.

Pilot study of fossil evidence of onshore-directed storm events in estuarine sediments: Chezzetcook Inlet, Nova ScotiaNatural Resources Canada Climate Change Impacts and Adaptation Program SST 20090027.

Sediment cores collected from the landward side of a baymouth barrier in a lower estuarine environment of Chezzetcook Inlet contain proxy “signals” of onshore-directed storms that are manifested by the sudden appearance of benthic and planktic Foraminifera species. These taxa have been eroded and transported from adjacent inner shelf open-marine environments. One relatively strong onshore-directed storm (hurricane?) event appears to have caused a reduction in seawater exchange in the southeastern part of the inlet that persisted for at least several decades. In this particular barrier-protected lower estuarine depositional environment, foraminiferal storm-indicator species distributions in older sediments seem to be spatially patchy. Consequently, in this Chezzetcook depositional setting, the successful reconstruction of a complete proxy storm record will require replicate coring and high-frequency core subsampling strategies.

Depositional Processes in an Anoxic, High Sedimentation Regime in the Saguenay Fjord

The sediment dynamics of north temperate estuaries are seasonally modulated by factors such as ice cover, wind speed, and by the magnitude of the spring freshet. Anomalous events such as landslides, storms or consecutive years of high rainfall are also responsible for significant variations in annual sediment transport and deposition rates in coastal marine environments. Bioturbation of sediments deposited in these environments usually obscures much of the sedimentary and paleontologic record, however large amounts of organic detritus can lead to low O2 concentrations in or above sediments, causing reduced benthic activity, and unconformities may be preserved. The head of Saguenay Fjord in Eastern Canada has been identified as an area where detrital organic input to sediments is comparatively high.

Monitoring in Coastal Environments Using Foraminifera and Thecamoebian Indicators: Conclusions and Final Remarks

Preface Scope of this book Who should read this book 1. Some perspective on Testate Rhizopods 2. Methodological considerations 3. Applications 4. Research on new applications 5. Freshwater systems applications 6. Conclusions and final remarks Appendix Glossary Taxonomic list of species Bibliography Name index Subject index.