Response of benthic foraminifera Rosalina leei to different temperature and salinity, under laboratory culture experiment

Abstract

Live specimens of benthic foraminiferal species Rosalina leei were subjected to a combination of temperature (25°C, 30°C and 35°C) and salinity (25‰, 30‰ and 35‰) to assess its differential response to the annual range of seawater temperature and salinity reported at the sampling site. A total of 216 specimens were used for the experiment. Within the range of temperature and salinity, to which R. leei specimens were subjected as part of the present experiment, growth increased with increasing salinity, whereas increase in seawater temperature resulted in retarded growth. Maximum growth was reported in the specimens kept at 25°C temperature and 35‰ salinity while the rest of the specimens maintained in 30‰ and 25‰ saline water, showed comparatively less growth. The specimens kept at 30°C and 35°C temperature and different salinities showed much less growth as compared to the specimens maintained at 25°C temperature. However, none of the R. leei specimens subjected to the present experiment reproduced during the course of the experiment. The absence of reproduction under the present set of temperature and salinity conditions, probably indicates that R. leei reproduces at a very narrow range of temperature and salinity which is different from the temperature and salinity conditions in the present experiment. It is further inferred that under the present set of temperature–salinity conditions, 25°C temperature and 35‰ saline water is most suitable for the growth of R. leei. Results are significant as the responses of benthic foraminifera to different temperatures and salinity are being used for palaeoclimatic reconstruction.

Difference in optimum temperature for growth and reproduction in benthic foraminifer Rosalina globularis: Implications for paleoclimatic studies

“…Our findings are also supported by Boltovskoy et al (1991) who summarized that decrease in temperature leads to smaller shells of the same species. This study also contradicts the findings of Nigam et al (2008) who noted that the specimens of Rosalina leei subjected to 25°C temperature showed more growth compared to the specimens subjected to 30°C and 35°C temperatures. This indicates that the species belonging to the same genus may have different temperature preferences.…”

“…Previously, it was observed that outside the reproductive temperature limits, the foraminifera remain alive and yet not reproduce and also that though foraminifera reach maturity, they reproduce only if the environmental conditions are favorable (Bradshaw 1955(Bradshaw , 1957. Nigam et al (2008) also noticed that, specimens of Rosalina leei did not reproduce at any of the temperatures to which they were subjected to in the laboratory (25ºC, 30ºC and 35ºC), but the specimens survived for longer time, as well as showed significant growth at all the three temperatures. They also suggested that none of the temperatures at which Rosalina leei was maintained in laboratory, was favorable for its reproduction.…”

“…This range of seawater temperature was selected based on continuous monitoring of physico-chemical parameters in the field from where live specimens were collected (Rodrigues, 1984;Nigam et al, 2008). Initially, all the specimens were kept at 27 °C temperature and 35 ‰ salinity as this was the temperature-salinity combination at which the specimens reproduced.…”

“…Both field and laboratory culture studies show that seawater temperature is among the few major seawater characteristics that affect benthic foraminiferal distribution and morphology in shallow water regions (Boltovskoy et al, 1991;Murray, 2006;Nigam et al, 2006;2008). Benthic foraminifera are known to tolerate a wide temperature range (-10 °C to 45 °C) (Murray, 2006).…”

Warmer more acidic conditions cause decreased productivity and calcification in subtropical coral reef sediment‐dwelling calcifiers

“…However, there is limited evidence of the effects of ocean warming and acidification in these two important carbonate sediment producers. Elevated seawater temperatures of 30uC to 35uC reduced the growth rate in the benthic foraminifera Rosalina leei Hedley and Wakefield (Nigam et al 2008) and induced algal symbiont loss in Amphistegina gibbosa d'Orbigny when temperatures reached 32uC (Talge and Hallock 2003). Borowitzka and Larkum (1976) showed an inhibition in calcification in Halimeda tuna (Ellis and Solander) Lamouroux when seawater pH was dropped from 8.0 to 7.5.…”