Timothy R. Parsons

An experimental simulation of changes in diatom and flagellate blooms

Abstract The sequence of events from a diatom to a flagellate bloom were simulated in a large sea-water enclosure. The two factors used to control the sequence were light and nutrients. The results indicate that diatom growth can be manipulated to occur under specific conditions of light intensity and nutrient concentrations. Once diatom growth has begun it appears to be more rapid than that of the flagellates. The importance of this experiment to the study of food chain Ecology in the sea is discussed.

The Wildlife Community of Iona Island Jetty, Vancouver, B.C., and Heavy-metal Pollution Effects

Marine and terrestial animals have been shown to be particularly abundant in a wildlife community associated with a marine sewer outfall from the City of Vancouver. These same animals are contaminated with high levels of heavy-metals but are apparently protected from their poisonous effects by the production of a protein known as metallothionein. The amount of metallothionein and heavy-metal loading appears to depend primarily on the degree of pollution and secondly on the species of animal and its position in the food-web.

The removal of marine predators by fisheries and the impact of trophic structure

Abstract Examples are given from the Atlantic, Pacific, and Antarctic Oceans of the effects of fisheries on marine ecosystems. The results show that the removal of predators may have various effects, including a replacement of exploited species by alternate species in the same trophic position, an increase in production at lower trophic levels, or, long term effects involving ecosystem change.

The distribution of organic carbon in a marine planktonic food web following nutrient enrichment

Abstract Low level nutrient enrichment of four enclosed water columns showed an increased production with nutrients but a decrease in transfer efficiency between primary producers and ctenophore production. From an extrapolation of primary productivity levels in the enriched containers to one unenriched container it is found that the nitrogen flux was ~ 1.52 mg-at. N/m 2 /day which allows for an approximate doubling of the nitrogen supply as calculated from winter nitrate levels. A carbon budget for each container was calculated for primary, secondary, and tertiary producers; decrease in transfer efficiencies were accounted for at various points in the food web.

Carbon dioxide partial pressures in North Pacific surface waters — Time variations

Observations were made of time variations of the carbon dioxide partial pressures (Pco2) of the atmosphere and surface sea waters in the Pacific subarctic region. Data were obtained on a cruise of the USC & GSSSURVEYOR in October, 1968 and on the TRANSPAC expedition of the CNAVENDEAVOUR in March–April, 1969. A rise in surface water Pco2 of 18×10−6 atm occurred in a period of 30–45 days in March–April due principally to spring warming of surface waters. An average increase of 60×10−6 atm occurred between October, 1968 and March, 1969 as a result mainly of cessation of summer phytoplankton production and the onset of winter-storm-driven vertical mixing. Because the air-sea Pco2 gradient not only changed appreciably in magnitude but also changed sign, there are important implications for calculations of air-sea exchange of carbon dioxide on the ocean wide scale.

Trophodynamic phasing in theoretical, experimental aud natural pelagic ecosystems

It is a great honour to be awarded the Oceanographical Society of Japan Prize for 1988 and to be provided with this opportunity to review our work on trophic relations in the pelagic environment of the sea. Many Japanese colleagues have participated in Canada on our experiments. These persons include Drs. H. Seki, M. Takahashi, A. Hattori, T. Ikeda, I. Koike, M. Ohtsu, S. Ichimura, K. Iseki, E. Matsumoto, N. Handa, Y. Maita, and others without whom our work on marine ecosystems would have assumed much less importance. In addition, the visit of Professor M. Uda to Nanaimo in 1959, and his lectures on fisheries oceanography, have always been an inspiration to me in the practical application of oceanography.For me, work on trophodynamic relationships grew out of my early association with Dr. J.D.H. Strickland who initiated some ecosystem studies using large plastic bags in the 1960s (Strickland and Terhune, 1961; Strickland, 1967). The CEPEX program (e.g. Parsons, 1978), which was started about a decade later, gave us the first real opportunity to break away from laboratory studies, where only species which generally grew best were studied, and to perform studies under near natural conditions on multiorganism communities. The purpose of this program was to provide some answers to practical problems as well as to gain a fundamental understanding of biological oceanographic processes. This program was started at a time when a large number of stories were circulating (e.g. Heyerdahl, 1975) that man was about to kill life in the oceans through pollution. In a practical sense what I believe that the CEPEX program showed was that the oceans were much more resilient than had been supposed. The effect of many kinds of pollutants tested during this program was to change the course of ecosystem interactions but not to cause the elimination of life. The scientific value of these experiments went much further in giving us time series data about how the physical/chemical environment interacts with different trophic levels. For the first time, the biological oceanographer was liberated from the hopeless entanglement of time and space in the sea, and it was now possible to follow population dynamics of planktonic organisms (Mullin, 1982).

The Future of Controlled Ecosystem Enclosure Experiments

The dangerin attempting to predict the future of science, or indeed any event, is that precise predictions can turn out to be inaccurate while woolly ones are next to useless. In the field of physics (Campbell 1939) it was formerly shown very precisely, using good mathematics, that space travel was not possible; yet de Nostradame (1568) was able to predict the space race 400 years earlier (if only someone had had the ability to understand exactly what it washe had predicted in the nebulous language of a prophet). Of these two glimpses of the future, I find the precise prediction, although inaccurate due to some wrong assumptions, to be the more informative. In fact, to be able to disagree with anexact conclusion is much of what research is all about. It is lack of belief in our current understanding of nature that drives the researcher to seek new explanations and, in so doing, to seek new ways to investigate the world around us. The driving force in the development of controlled aquatic ecosystems has been a desire to bridge a gap between the size scales of laboratory experiments and field observations (Strickland 1967).

Tidal wake-mixing: localized effects on primary production and zooplankton distributions in the Strait of Georgia, British Columbia

Abstract A promontory-induced shear-layer mixing event was examined for effects of nutrient concentrations in the euphotic zone of the Strait of Georgia, British Columbia, Canada. Increases of nitrate within individual mixing events resulted in increases in “new” primary production. Samples were obtained to examine the resultant net increase in primary production in individual mixing events. Mean production in the mixed samples was determined to be 67.4 mg C·m−3 compared to 13.1 mg C·min−3 in the stable water column samples (sampling depth of 1 m) during the same 3-day incubation period. Estimates from existing current meter and horizontal mapping data examining this mixing feature, give estimates of mixing volumes which could result in a net increase in “new” production of 4.8–82 t of phytoplankton C in June and July of 1986, with a mean increase of 33 t. The resultant increase in primary production (mean 33 t could theoretically result in 6.6–14.9 t of secondary production in the region during this 2-month period. Densities of copepods and total zooplankton were determined to be significantly (P≤0.05) higher in the mixed water compared to the stable water mass, when wind mixing did not break down stratification. Copepod nauplii densities were significantly greater in the mixed water when compared to the stable water column in June (P≤0.05) with no significant differences in densities observed during the July and August sampling periods. It is proposed that increases in surface zooplankton densities are due to the mixing of zooplankton population associated with the chlorophyll maximum.

Addition of Nutrients to a Lake Leads to Greatly Increased Catch of Salmon

The Great Central Lake story from British Columbia provides an interesting microcosm which touches on a variety of Mans activities. Other aspects which have not been discussed but were touched upon during the course of the experiment include logging, mining, hydroelectric power, recreational activities, and drinking-water. These ‘resources’ are also part of Mans use of the Great Central Lake system.

Estuarine microplankton: An experimental approach in combination with field studies

Abstract In the natural environment, seasonal climatic changes have the dominant effect on phytoplankton productivity. Salinity effects in estuarine habitats are, however, probably equally important but cannot usually be separated from seasonality. The use of microcosms allows the salinity effect to be studied independent of seasonality. Results of a year-long field study in the Fraser River estuary, British Columbia, Canada, are presented and compared with results of laboratory experiments. In a series of flasks (201 volume), natural low and high salinity waters were mixed in order to give salinities of ⩽ 5, 10, 18, and ⩾ 26%.. The mixed waters were enriched so as to simulate the entrainment of nutrient-rich, saline water in a salt wedge estuary. A distinct pattern of autotrophic and heterotrophic growth developed resembling natural events in the Fraser River estuary during the period between winter and late spring. The salinity values influenced the microplankton ecology with respect to phytoplankton species composition and total biomass. Despite seasonal variability of the source waters, the simulated spring bloom was reproducible under constant laboratory conditions, thus allowing the continued performance of experiments. The microcosms were useful in simulating natural events as well as in testing the impact of natural and man-made perturbations. In the experiments presented, naturally occurring perturbations had a much greater impact on estuarine ecology than addition of anthropogenic pollutants in concentrations much higher than known to occur in moderately polluted estuaries.