The experiments began on September 23, 2003 and continued for 210 days ending on April 19, 2004. At that time none of the original individuals from nine species, (eight genera), remained alive in the experimental systems, however there were individuals alive in the control system at this time. The systems were then maintained at the final salinity and temperature so that follow-up observations could be made on any offspring that were noted. Table 1 shows the duration of the experiments, and the final salinities obtained when all starting individuals were dead. Table 2 shows the duration of groups based on hyper/hypo saline systems. The following results are organized alphabetically by species and explain the response of each species to the four experiments. The salinity levels for each experiment are in parts per thousand (ppt) and all temperatures are in degrees Centigrade. The levels indicated are the final averages (FA), i.e. the, last ten days’ average of the measurements, prior to the death of the last individuals (of a given species) in each experimental system. The high/low salinity systems are referred to as the hypersaline/hyposaline systems respectively.

Table 2. Duration data for the experimental systems. Survival is in days for individual species in each of the experimental systems

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Brachidontes exustus: B. exustus is commonly found throughout Florida Bay, in a wide range of salinities and temperatures, and is often seen in dense groupings. The individuals in the hypersaline, high temperature System 1 (FA 59 ppt and 31°C) survived for 181 days, with no juveniles observed. Individuals in the high saline low temperature System 2 (FA 57 ppt and 15°C) survived for 159 days and no juveniles were seen (Figure 13A). Individuals placed in the hyposaline, high temperature System 3 (FA 16 ppt, and 33°C) survived for 154 days and no offspring were observed. The individuals in low salinity and low temperature, System 4, (FA 18 ppt and 17°C) survived for 149 days and no offspring were observed. (Figure13B) B. exustus individuals in the control system were alive more than 180 days beyond the termination of the experimental phase and have reproduced effectively.

Bulla striata: B. striata is often seen live and is abundant as pristine shell debris from the marginal areas (regions near the Everglades/ Florida Bay interface) of Florida Bay. The experimental results confirm the resilience of B. striata to a broad range of salinity and temperature values. B. striata individuals survived for 180 days in increasing salinity and increasing temperature System 1, (FA 58 ppt and 31°C), with juveniles observed in the system on 2/18/2004. The individuals in the increasing salinity and decreasing temperature System 2 (FA 58ppt and 17.51°C) survived for 175 days with juveniles recorded on 12/22/2003 (Figure 14A). The hyposaline higher temperature individuals System 3, (FA 19 ppt and 33°C) were alive for 131 days with no juveniles seen. The individuals in the hyposaline, low temperature System 4, (FA 16 ppt and 18°C) survived for 159 days with no juveniles found (Figure 14B). Seventy percent of the original individuals were alive in the control system at the termination of the experiment. Reproduction in the control system was observed in large numbers. B. striata was resilient across the experimental range and had an abundance of juveniles appearing in the hyper-salinity tanks within 150 days. Salinities when the juveniles were first seen were 45-50 ppt, and these new individuals remain in the systems one year later.

Cerithium sp. cf. C. eburneum: C. sp. cf. C. eburneum is more commonly found in the outer estuarine to marine waters where salinity and temperature extremes are less frequent. As expected, this species had a relatively low tolerance for changes in salinity and temperature. All of the original test individuals were dead within 149 days in the hypersaline, high temperature System 1 (FA 50 ppt and 28°C) with no reproduction observed. The individuals in hypersaline low temperature System 2 (FA 38 ppt and 18°C) survived for 120 days and no offspring were observed (Figure 15A). The hyposaline high temperature System 3 (FA 25 ppt and 28°C) individuals survived for 96 days with no offspring seen. The individuals in the hyposaline, decreasing temperature System 4 (FA 25 ppt and 18°C) survived 92 days with no juveniles observed (Figure 15B). The control system also lost most of the original individuals (possibly due to a temperature spike causing stress on 12/22/03. There were, however, juveniles seen in the control system on 01/14/2004 and 3/17/2004. The offspring are still present and growing one year later.

Cerithium muscarum: C. muscarum proved to be very resilient in all trial scenarios. The individuals in the hypersaline, high temperature System 1 (FA 62 ppt, and 34°C), survived for 200 days, and juveniles were observed throughout the experimental system by 1/30/2004. The juveniles remain in the system one year later and are reproducing as well. The individuals that were placed in the hypersaline, low temperature System 2 (FA 57 ppt, and 17°C) survived for 172 days, and juveniles were observed in the system on 1/26/2004 and remain in the system one year later (Figure 16A). The hyposaline, high temperature System 3 (FA 17 ppt, and 33°C) individuals survived for 152 days and no juveniles were observed. The individuals placed in the hyposaline, low temperature System 4 (FA 16 ppt, and 16°C) survived for 159 days with no reproduction observed (Figure 16B). Sixty five percent of the original individuals remained alive in the control system at the termination of the experiment. C. muscarum has been observed in a wide range of salinities and temperatures in situ so these results were not unexpected; however, the proliferation and resilience of the offspring throughout all of the tanks within a system, including the refugia was unexpected.

Chione cancellata: C. cancellata is found commonly throughout Florida Bay and surrounding marine waters. These experiments were in large part designed to determine the range of salinity tolerance of C. cancellata. The individuals in the hypersaline, high temperature System 1 (FA 57 ppt and 31°C) survived for 161 days and no juveniles were seen. The hypersaline low temperature System 2 (FA 53 ppt and 16°C) individuals were alive for 142 days with no offspring found (Figure 17A). The individuals in the hyposaline high temperature System 3 (FA 19 ppt and 31°C) survived for 139 days and no juveniles were found. The individuals in the hyposaline low temperature System 3 (FA 20 ppt and 15°C) survived for 144 days with no juveniles observed (Figure 17B). Fifty percent of the individuals in the control system, maintained at marine salinities and temperatures, survived beyond the completion of the experimental phase.

Columbella rusticoides: C. rusticoides is found throughout Florida Bay and into the surrounding obligate marine regions. While the number of individuals observed in situ is limited, this species has been observed in a range of salinities and temperatures. The individuals in the hypersaline, high temperature System 1 (FA 61 ppt, and 32°C) survived for 186 days with no juveniles found. The hypersaline, low temperature System 2 (FA 53 ppt, and 16°C) individuals survived for 141 days with no reproduction observed (Figure 18A). The individuals placed in the hyposaline, high temperature System 3 (FA 23 ppt, and 33°C) survived for 124 days with no juveniles found. The hyposaline, low temperature System 4 (FA 24 ppt, and 15°C) individuals survived for 89 days with no reproduction observed (Figure 18B). Thirty percent of the control system individuals survived beyond the close of the experimental phase, and a small group of juveniles were observed.

Modulus modulus: M. modulus is commonly found throughout Florida Bay and in widely varying salinities and temperatures. The hypersaline, high temperature System 1 (FA 61 ppt, and 32°C) individuals survived for 190 days but no offspring were observed. The hypersaline, low temperature System 2 (FA 57 ppt, and 17°C) individuals survived for 172 days and juveniles were observed throughout the entire system including the refugium tank on 2/18/2004 (Figure 19A). The individuals in the hyposaline, high temperature System 3 (FA 17 ppt, and 32°C) survived for 152 days with no juveniles observed. The hyposaline, low temperature System 4 (FA 21 ppt, and 15°C) individuals survived for 141 days with no juveniles observed (Figure 19B). Fully sixty percent of the original individuals in the control system were alive at the end of the experimental phase, and of these fifty percent were alive over one year later. Juveniles have spread throughout the entire system and have been utilized to begin other experiments.

Prunum apicinum: P. apicinum is a common inhabitant of seagrass beds throughout Florida Bay and Biscayne Bay, and has been observed in a range of salinities 25-45 ppt. The individuals in the hypersaline and high temperature System 1 (FA 60 ppt and 33 ° C) survived for 191 days and no offspring were observed. The individuals in the hypersaline, low temperature System, (FA 49 ppt, and 24°C) survived for 87 days with no reproduction observed (Figure 20A). The individuals in the hyposaline, high temperature System 3 (FA 20 ppt and 33 ° C) survived for 131 days with no reproduction observed. The hyposaline, low temperature System 4 (FA 28 ppt and 23°C) individuals survived for only 57 days (Figure 20B). Three out of five individuals in the control system survived beyond the termination of the experimental phase but reproduction was not observed. The die-off of P. apicinum in this experiment may be more due to lack of proper food source than to the salinity/ temperature levels at the time of demise.

Turbo castanea: T. castanea is widely distributed in Florida Bay and in obligate marine waters throughout South Florida. It is a good indicator of stable average salinities and provides a euhaline comparison to the overall experimental results. The individuals in the hypersaline, high temperature System 1 (FA 51 ppt and 29°C) survived for 124 days, with no observed offspring. The individuals in the hypersaline, low temperature System 2 (FA 47 ppt, and 23°C) survived for 93 days with no reproduction observed (Figure 21A). The individuals placed in the hyposaline, and high temperature System 3 (FA 24 ppt, and 34°C) survived for 122 days with no observed reproduction. The hyposaline, low temperature System 4 (FA 27 ppt, and 20°C) individuals survived for 64 days with no juveniles observed (Figure 21B). The control system had a survival rate of nine out of the original ten individuals and reproduction in very high numbers.

Examining the results for all the species in the four experiments, it appears that salinities higher than 35 ppt (typical marine) and below 45 ppt have a minimal overall effect on the nine species tested (experiments 1 and 2). When the salinity values exceeded the 45 ppt range, however, mortality rates began to increase. Conversely, in the lower salinity experiments (3 and 4) a decrease of just 9 ppt from 35 ppt to 26 ppt had an immediate effect on the mortality rate in almost all species tested. In contrast to salinity, temperature appears to be a secondary stressor in all of the experimental scenarios. In experiment 3 and 4 the temperature oscillations within the experimental systems did not exceed typical conditions in Florida Bay when the die-off of multiple species began. However, rapid temperature changes seen in experimental mesocosms 1 and 2 on 12/27/2003 in System 1 and 12/29/2003 in System 2 clearly added a level of stress. The die-off of several individuals in both Systems 1 and 2 following the rapid temperature changes demonstrates the effect that wide range-short duration temperature changes have on these species. (Figure 22 of all graphs). These temperature fluctuations are also observed in situ and clearly need further experimentation in order to quantify slow stressors coupled with rapid change stress.

Figure 13A. Brachidontes exustus % remaining alive within the experimental systems. [larger image] Figure 13B. Brachidontes exustus % remaining alive within the experimental systems. [larger image]

Figure 14A. Bulla striata % remaining alive within the experimental systems. [larger image] Figure 14B. Bulla striata % remaining alive within the experimental systems. [larger image]

Figure 15A. Cerithium sp. cf. C. eburneum % remaining alive within the experimental systems. [larger image] Figure 15B. Cerithium sp. cf. C. eburneum % remaining alive within the experimental systems. [larger image]

Figure 16A. Cerithium muscarum % remaining alive within the experimental systems. [larger image] Figure 16B. Cerithium muscarum % remaining alive within the experimental systems. [larger image]

Figure 17A. Chione cancellata % remaining alive within the experimental systems. [larger image] Figure 17B. Chione cancellata % remaining alive within the experimental systems. [larger image]

Figure 18A. Collumbella rusticoides % remaining alive within the experimental systems. [larger image] Figure 18B. Collumbella rusticoides % remaining alive within the experimental systems. [larger image]

Figure 19A. Modulus modulus % remaining alive within the experimental systems. [larger image] Figure 19B. Modulus modulus % remaining alive within the experimental systems. [larger image]

Figure 20A. Prunum apicinum % remaining alive within the experimental systems. [larger image] Figure 20B. Prunum apicinum % remaining alive within the experimental systems. [larger image]

Figure 21A. Turbo castanea % remaining alive within the experimental systems. [larger image] Figure 21B. Turbo castanea % remaining alive within the experimental systems. [larger image]

Figure 22. Click on the graphs in each column to view a larger version.