Heavy metal level keeps increasing in the environment. One of them, in the aquatic environment. This increase was caused by human activities in various fields. It is indicated by an increase in copper (Cu) levels in the sea by 9 x 10 6 tons per year (Pinto et al., 2003).
Cu is one of the important elements needed by organisms (Soegianto et al., 2013) including microalgae for photosynthesis needs, but if the concentration of Cu is too high it will cause phytotoxicity in cells and significantly inhibit cell growth, and even cause the death of microalgae (Yan and Pan, 2002). Furthermore, level of Cu that is too high in the aquatic environment can reduce the growth rate and pigment content of microalgae (Saeza et al., 2015), which will increase reactive oxygen species (ROS) produced by disruption of Cu ions in the Fenton reaction (Okamoto et al. ., 2001). Increased levels of ROS or free radicals can attack nucleic acids, proteins and lipids and cause permanent metabolic dysfunction and rapid cell death (Gill and Tuteja, 2010).
Another heavy metal that also increased in concentration is cadmium (Cd). Cd is an element whose biological functions are not yet known (Babich and Stotzky, 1978; Nursanti et al. 2017). Cd levels in the natural environment are usually in low concentrations around 0.18 ppm, and are derived from mineral components in the earth’s crust (Iverson and Brinckman, 1978). Cd levels in fresh water are in the range of 0.5 ppb and 0.1 ppb in seawater (Henriksen and Wright, 1978).
Cd can enter the environment from various anthropogenic sources such as byproducts from zinc refining, coal burning, mine waste, steel coating, production of iron and steel, fertilizers, and pesticides. The use of Cd in various industries has accelerated the rate of biological mobilization and transportation of these elements because the Cd input to the environment exceeds the amount involved in the natural abiotic cycle process (Babich and Stotzky, 1978).
High levels of Cd can be found in sewage sludge, plants, plankton and invertebrates. In addition, Cd toxicity is highly dependent on metal speciation, as well as various physical, chemical, and biological factors (Babich and Stotzky, 1980). Heavy metals Cd and Cu have phytotoxic characteristics when they are in a high concentration aquatic environment. Nassiri et al. (1997), stated that Cu and Cd have high levels of toxicity to the growth of Skeletonema costatum.
Skeletonema costatum is a common plankton species that is usually found, especially in coastal estuaries and marine environments where they often form aggregates. This species is morphologically plastic, genotypically diverse, physiologically versatile, and is found throughout the world except the Antarctic ocean (Kooistra et al., 2008). Phytoplankton are dominated by microalgae where they play an important role in the balance of the marine ecosystem and are at the bottom level of the food chain so microalgae will have the most influence due to exposure to heavy metals (Zeitzchel, 1978). One of the impacts of heavy metals presence in the aquatic environment is a decrease in the growth rate of microalgae because this species is very sensitive to foreign substances (Stachowski, 2008). Therefore, this study aimed to determine the response of microalgae, Skeletonema costatum, growth due to the presence of heavy metals in the environment.
In this study, Skeletonema costatum microalgae were exposed to Cd and Cu at concentrations 0 (control), 7, 1.3, and 1.9 ppm with 3 replications for 96 hours. Measurement of microalgae density is done every 12 hours to monitor the growth of microalgae during recovery. IC 50 values (concentrations of Cd and Cu that can inhibit the growth of S. costatum by 50 percent) are 0.419 ppm for Cd and 1.046 ppm for Cu. In other words, lower levels of Cd are more toxic than Cu.
Details of research available at paper titled:
“CADMIUM AND COPPER TOXICITY TEST AS GROWTH INHIBITOR OF SKELETONEMA COSTATUM
GUNTUR, DWI CANDRA PRATIWI, NIKEN PRATIWI, DEFRI YONA, RESPATI DWI S, RARASRUM DYAH K, DAN AGOES SOEGIANTO