The Effect of CO2 Concentrations on Blue Mussel (Mytilus Edulis) Behaviour, Health, Mortality and Detachment Rates: a New Potential Way of Anti-Fouling
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The effect of CO2 concentrations on blue mussel (Mytilus edulis) behaviour, health, mortality and detachment rates: a new potential way of anti-fouling Name Kees te Velde Student nr. 930428862090 Supervisors Celia (Yuzhu) Wei, Edwin Foekema & Tinka Murk Chair group Marine Animal Ecology Date 16-12-2018 mussel displacement was recorded in order to Abstract determine movement activity. In a second Fouling organisms on ship’s hulls increase experimental study, M. edulis was exposed to hydrodynamic drag of the vessel and decrease several degrees of CO2 induced acidified water speed and fuel efficiency which has large conditions at pH 6.2, 6.8, 7.2, 7.6 and 8 economic impacts for shipping companies. The (control) for 21 days. Mortalities were recorded GasDrive project is developing an innovative throughout the experiment and a novel ship, with a more than 50% reduced fuel experimental setup was designed to determine demand compared to traditional ships. The detachment velocities. Mussel health was assessed through the following factors: Shell exhaust, mainly consisting of water and CO2, will be released under the ship’s hull. A great strength, growth rates, reaction time (the time deal of research has been conducted of the it takes a mussel to close its shell in response to a disturbance) and feeding rates. negative effects of future CO2 levels on calcifying organisms due to anthropogenic CO2 induced acidification to pH 6.2 resulted in a carbon emission. However, a locally elevated 35% reduction in M. edulis shell strength and a CO2 concentration has never been suggested as 5 fold increase in reaction time. A trend was a means of anti-fouling. The combination of seen between mortality and pH, with a 10% CO2 exhaust gasses on the ship’s hull and the increased mortality rate at pH 6.2 and 6.8. water forces past the moving vessel, may turn Also, a trend was visible with lower feeding out detrimental to fouling organisms, causing rates at reduced pH. No significant effect of mortality and detachment. Therefore, GasDrive elevated CO2 was found on movement activity, may prove a novel anti-fouling strategy. growth rates and detachment velocities. As we aim to discover whether the GasDrive In conclusion, if around a ship hull that is CO2 output may have anti-fouling properties, covered by mussels the pH is decreased to as we must understand the effect of both CO2 and low as 6.2, it would take more than a month for water velocities on fouling bivalves. CO2 can the mussels to show significant mortality rates. cause detachment of bivalves from a vessel in However, if CO2 was to be used in combination three ways: Through mortality, lowered with toxic paints, mortality rates may probably attachment strength leading to a reduction in drastically increase. We therefore recommend detachment velocity (the maximum water the use CO2 as an anti-fouling strategy when velocity an organism can resist before it dealing with marine bivalves in combination detaches from the substrate) or avoidance with pre-existing methods to increase behaviour. Mytilus edulis was chosen as a effectiveness. Thereby reducing the required model organism for marine fouling bivalves. concentrations of toxic compounds in paints, This brings us to the following research and lowering environmental impact. question: How do elevated CO2 concentrations affect M. edulis activity, health, mortality and Also, shell strength and reaction time are both detachment velocities? We hypothesised that important features that protect mussels from elevated CO2 concentrations will decrease M. predation and they are negatively affected by edulis health and detachment velocities and increased CO2 concentrations. This may greatly increase mortality and movement activity. affect vulnerability to predation. If there is a sufficient amount of predators around a M. edulis was exposed to several degrees of GasDrive ship, the abundance of mussels on the CO2 induced acidified water conditions at pH hull may be greatly reduced. 6.5, 7.5 and 8 (control) for 4 days. Twice a day, Index Abstract ................................................................................................................................................... 2 Introduction ............................................................................................................................................. 4 Materials & Methods .............................................................................................................................. 5 Sampling and preparation ................................................................................................................... 5 Experimental procedure behaviour experiment ................................................................................. 6 Experimental procedure long term exposure ..................................................................................... 7 Data analysis ............................................................................................................................................ 9 Behaviour experiment ......................................................................................................................... 9 Long term exposure experiment ......................................................................................................... 9 Results ................................................................................................................................................... 10 Behaviour experiment ....................................................................................................................... 10 Long term exposure experiment ....................................................................................................... 11 Discussion .............................................................................................................................................. 12 Behaviour .......................................................................................................................................... 12 Attachment strength ......................................................................................................................... 13 Mortality ............................................................................................................................................ 13 Overall health .................................................................................................................................... 14 Method reflection ............................................................................................................................. 14 Conclusion ............................................................................................................................................. 16 Suggestions ............................................................................................................................................ 16 References ............................................................................................................................................. 17 Appendix 1: Mussel feeding simulation R script ................................................................................... 20 Appendix 2: Water parameters of the long term exposure experiment .............................................. 22 Appendix 3: Ratio of detached mussels with increasing water velocity. .............................................. 23 Introduction it reacts with H2O to form carbonic acid (H2CO3), which in turn results in titration of Bio-fouling is defined as “the colonisation of - carbonate ions (HCO3 ) [9]. As pH in seawater is aquatic organisms on ships and platforms” [1]. largely determined by the ratio of carbonic acid Two groups of bio-fouling organisms can be to carbonate ions and ΩCaCO3 (calcium distinguished, micro-foulers (e.g. Bacteria, carbonate saturation state) is driven by the Algae and Fungi) and macro-foulers (e.g. total amount of carbonate ions, this leads to a Barnacles, Bivalves, Algae and Bryozoans). reduction in seawater pH and ΩCaCO3 [9]. ΩCaCO3, Bivalves are one of the major groups of macro- is a measure of the potential for calcium fouling organisms [1]. Fouling organisms on carbonate to dissolve [9]. A large group of ship’s hulls increase the friction of the vessel marine organisms utilize calcium carbonate as and have been estimated to decrease speed by the primary mineral for the formation of shells approximately 2% and reduce fuel efficiency up and skeletons (calcifying organisms). As ΩCaCO3 to 45% [2, 3]. This costs shipping companies decreases, shell dissolution starts to occur, enormous amounts of money [3]. In addition to which impacts shell strength [10] and requires the economic impacts due to increased fuel higher allocation of energy to calcification [11]. demand, biofouling on ships is one of the most A great deal of research has been conducted of important vectors for the invasion of the negative effects of future CO2 levels on nonindigenous species [4]. These non-native calcifying organisms due to anthropogenic species occur globally, they are associated with carbon emission [11]. However, a locally negative impacts that affect ecosystem elevated CO2 concentration has never been structure and functioning and cause suggested as a means of anti-fouling. The environmental impacts and economic damage combination of CO2 exhaust gasses on the [5]. Anti-fouling can reduce the spread of these ship’s