Influence of Potentially Confounding Factors on Sea Urchin Porewater Toxicity Tests

Abstract

The influence of potentially confounding factors has been identified as a concern for interpreting sea urchin porewater toxicity test data. The results from >40 sediment-quality assessment surveys using early-life stages of the sea urchin Arbacia punctulata were compiled and examined to determine acceptable ranges of natural variables such as pH, ammonia, and dissolved organic carbon on the fertilization and embryological development endpoints. In addition, laboratory experiments were also conducted with A. punctulata and compared with information from the literature. Pore water with pH as low as 6.9 is an unlikely contributor to toxicity for the fertilization and embryological development tests with A. punctulata. Other species of sea urchin have narrower pH tolerance ranges. Ammonia is rarely a contributing factor in pore water toxicity tests using the fertilization endpoint, but the embryological development endpoint may be influenced by ammonia concentrations commonly found in porewater samples. Therefore, ammonia needs to be considered when interpreting results for the embryological development test. Humic acid does not affect sea urchin fertilization at saturation concentrations, but it could have an effect on the embryological development endpoint at near-saturation concentrations. There was no correlation between sediment total organic carbon concentrations and porewater dissolved organic carbon concentrations. Because of the potential for many varying substances to activate parthenogenesis in sea urchin eggs, it is recommended that a no-sperm control be included with every fertilization test treatment.

Sediment quality assessment in tidal salt marshes in northern California, USA: An evaluation of multiple lines of evidence approach

“…Total ammonium as nitrogen ranged from 1.96 to 10 mg/L (Table 1). Concentrations of unionized ammonia, which is the most toxic fraction of ammonia, ranged from 22.4 to 226 μg/L, falling within a range typically observed in field-collected porewater samples (Carr et al, 2006).…”

“…However, naturally-occurring toxicants, such as unionized ammonia, in pore water may change markedly from one day to the next due to tidal flushing, salinity changes, and hypoxia so the timing of sampling is a critical factor in conducting porewater toxicity tests and surveying benthic invertebrate communities. It is important to measure these natural variables to better interpret the results of toxicity tests (Carr et al, 2006). To minimize such artifacts, a total of 22 stations in intertidal areas were sampled in the four marshes between August 11 and 15, 2003.…”

“…Various types of toxicity tests (e.g., sea urchin embryo tests, amphipod survival tests) that have been used for the SQT approach typically measure short-term responses in laboratoryincubated embryos or small fauna exposed under laboratory conditions; so, they have limitations in linking the observed responses to the ecology of diverse resident species such as fish and crabs. In addition, the laboratory toxicity tests are subject to interferences from ammonia and sulfides that may be elevated in many estuarine systems (Carr et al, 2006;Phillips et al, 1997), including the salt marshes that were a focus of the present study.…”

Temperature modulates the response of the thermophilous sea urchin Arbacia lixula early life stages to CO2-driven acidification

“…The sub-Antarctic species Arbacia dufresni experienced a delay in development when raised at low pH with no effect on survival (Catarino et al, 2012b). Carr et al (2006) showed that pH tolerance limits for the fertilization and embryological development (2 days) of A. punctulata were 6.9e8.8.…”

CO2-induced fertilization impairment in Strongylocentrotus droebachiensis collected in the Arctic

“…The restriction of the fertilization success only to this criterion may lead to possible confounding results as the morphological features of fertilization success vary in different sea urchin species. In addition, there is a long list of substances that can initiate parthenogenesis on eggs leading to FE increase without being fertilized (Carr et al 2006;Levitan 2004). Also, in species such as S. franciscanus, polyspermic eggs do not raise the FE (vitelline envelope) and do not differ from unfertilized eggs (Levitan 2004).…”