A short life‐cycle test with the epibenthic copepod Nitocra spinipes for sediment toxicity assessment

Abstract

A new short life-cycle test methodology is presented to evaluate sublethal effects of contaminated sediments to the harpacticoid copepod species Nitocra spinipes. The method combines a 4-d survival-gravidity test with a 7-d development test. For water-only Cu exposures, the sensitivity of the development test endpoints were compared with tests using nonexposed gravid females to initiate the 7-d development test phase, and also with a multiple generation test comprising three successive phases: 9-d development; 21-d survival-gravidity; second-generation 9-d development. The results indicated that the development endpoints were the most sensitive, with median effective concentration (EC50) values of 95 µg Cu/L for nauplii/gravid female and 101 µg Cu/L copepodites/gravid female endpoints, followed by the gravidity (144 µg Cu/L) and survival (347 µg Cu/L). The sensitivity of the short life-cycle test endpoints was similar to the multiple-generation test endpoints, and the shorter test had less variability in controls. The multiple-generation test showed a large amount of stimulation of reproduction and development at Cu concentrations of 50 to 100 µg/L. The suitability of the short life-cycle test for assessing sediment toxicity was demonstrated using Cu-spiked and naturally contaminated whole sediments. Although the small nauplii were more difficult to isolate from sediments, the small amounts of sediments used for the tests and the large effects of the contaminated sediments on nauplii and copepodite numbers resulted in significant differences to controls. For sediment exposures, the sensitivity of the endpoints was in the order development > gravidity > survival. The short life-cycle test was demonstrated to detect, within 11 d of exposure, similar levels of effects on reproduction and development to those detected using a 39-d multiple-generation exposure.

Performance and sensitivity of rapid sublethal sediment toxicity tests with the amphipod Melita plumulosa and copepod Nitocra spinipes

“…Recently, test procedures have been developed that rapidly assess the potential for chronic effects from sediment contaminants to M. plumulosa [10] and N. spinipes [11]. Both methods are suitable for assessing effects on reproduction and survival following exposure to whole sediments for just 10 d, which is considerably shorter than the 20 to 28-d periods used in most sublethal sediment toxicity tests [9,16].…”

“…Toxicity tests can be conducted for acute or chronic exposure durations. While acute toxicity methods that assess the survival of amphipods after 10 d are by far the most commonly used [5,6], chronic tests are generally considered to be more sensitive to contaminated sediments [7][8][9][10][11].…”

Sediment biotesting in the Baltic Sea

“…Using widespread zooplankton species, biotests applying the epibenthic harpacticoid copepod Nitocra spinipes have been developed (Perez-Landa and Simpson, 2011), also in the Baltic Sea (Ribbenstedt et al, 2017). This organism has been extensively used to study the effects of a wide range of environmental contaminants using physiological, developmental and reproductive endpoints as well as responses in population growth and genetics (Ribbenstedt et al, 2017).…”

Avoidance of contaminated sediments by an amphipod (Melita plumulosa), A harpacticoid copepod (Nitocra spinipes), and a snail (Phallomedusa solida)

“…These sediments had low or negligible concentrations of metal and organic contaminants and have been demonstrated to not cause toxic effects to the organisms used in the study [24,25]. The surface layers (upper 2-4 cm) of sediments were collected using clean Teflon spatulas and presssieved through a 1.1-mm mesh on-site to remove coarse materials.…”

“…All of these species are known to graze or ingest sediment particles, making them suitable candidates for sediment toxicity testing [22][23][24]. For each species the influence of varying physicochemical properties of the sediment on the distribution of test organisms and the optimal exposure time to measure an avoidance response elicited by contaminated sediments were initially determined.…”