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Invasion of Ctenophore

Invasion of Ctenophore in the Philippines
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  Invasion of the Ctenophore Species All ctenophores are predators (Pechenik, 2009). Ctenophore densities population can  become quite high, particularly in coastal waters. As carnivores, ctenophores are most likely to have substantial impact on the abundance and population dynamics of other zooplankton (Greene et al., 1986). These ctenophores have significant ecological impact in their invaded aquatic system. They have been widely popular in terms of research that involves the discussion of specific ctenophores, its mechanisms and effects in the ecosystem. Based on the articles we read, there are several research studies that were conducted to give a detailed look for the ctenophore species, specifically  Mnemiopsis leidyi.    Mnemiopsis leidyi is a lobate ctenophore that occupies coastal water    with a wide latitudinal range (Costello and Mianzan, 2003) that poses a threat to ecosystems worldwide, and can even cause economic damage (Boersma, Hamer, and Malzahn, 2011). It invaded the Black Sea, the Mediterranean and the Caspian Sea due to its highly versatile planktonic predator capability (Costello and Mianzan, 2003; Boersma, Hamer, and Malzahn, 2011).  M. leidyi  was first recorded in the North Sea, yet its ecological impact is still completely unexplored (Boersma, Hamer, and Malzahn, 2011). However, it was found abundantly in high saline areas of Baltic Sea (Jaspers et al., 2013). In the study formulated by Gorokhova and colleagues, they demonstrated the essentiality of quantitative sampling that includes ctenophore larvae and eggs in understanding the population composition, recruitment processes and hence, the population dynamics of the invasive  M. leidyi  and  Mertensia ovum , as they are the most prominent ctenophores in the Baltic Sea .  M. leidyi  have dominated the population in the Baltic Sea but in relation with salinity, station, and season (Jaspers et al., 2013). Studies are now in progress to assess the effects of these recent invasions (Boersma, Hamer, and Malzahn, 2011). In understanding the trophic impacts of the  M. leidyi and its abundance and distribution at the sea, several methods were done like:   acoustic method, and conventional net sampling of the water column guided by acoustic data. Acoustic method is used to record distribution patterns by low-frequency acoustic system. The most informative combination of quantitative methods involves direct net sampling guided by acoustic data. The choice of sampling depends upon a variety of factor affecting study situations. However, vertical migration and the formation of near  bottom aggregation can affect abundance patterns, as well as our understanding of trophic interaction involving ctenophores. Whatever the sampling approach selected,  M. leidyi  distribution and abundance patterns should consider the potential for near bottom aggregation and vertical migration (Costello and Mianzan, 2003). Other ctenophore species were discovered in certain aquatic system.  Mertensia ovum was  present year round throughout the brackish Baltic Sea but also occurred in high saline areas during cold seasons.  M. ovum was distributed in surface waters or throughout the water column in spring and winter, but resided at depth during summer and autumn (Jaspers et al., 2013).   M. leidyi  is located one trophic level above the indigenous ctenophore  Bolinopsis infundibulum , whereas its trophic position was more similar to another native ctenophore,  Pleurobrachia pileus . Although  B. infundibulum  and  M. leidyi  are similar in size in prey-catching strategy, based on the stable isotope data, they did not compete for food; thus,  B. infundibulum  and  M. leidyi  occupied completely different trophic niches.  B. infundibulum  could well have srcinated from a different area where they had been feeding on lower organisms in the food chain (algae, protozooplankton) and  M. leidyi  probably prefers metazoan prey like  planktons. The main diet of all three ctenophores,  M. leidyi ,  B. infundibulum and  P. pileus,  was the large zooplankton fraction. However, there is a substantial predation on fish eggs by the indigenous  P. pileus , especially in March/April, and  based on the averages, fish eggs did not occur in the diet of  M. leidyi   at all, as they probably were rejecting fish eggs for copepods. Based on this, the study concluded that if any ctenophore species is a threat to the fish populations around Helgoland in the North Sea, it is the endemic species  P. pileus  and not the invasive  M. leidyi.    M.leidyi  at present is unable to affect the ecosystem in the North Sea in a similar way as it did in the Black Sea, and as a result, it might fit into the current food web without the catastrophic impacts observed in other invaded seas (Boersma, Hamer, and Malzahn, 2011). Ecosystem alterations and consequences for biodiversity have been documented (Carlton and Geller, 1993; Kideys, 2002) with disturbed aquatic systems being especially vulnerable to invasions (Richardson et al., 2009; Crooks et al., 2011). The ecological impacts include regime shifts and large-scale cascading effects throughout marine food webs, as documented for successfully established invaders (Kideys, 2002; Sorte et al., 2010). Ctenophores are marine invaders that harm the other species population in the system. Since these organisms are all  predators, their occurrence can caused shortage for food source of other species, particularly fish. Hence, ctenophore species’ invasions threaten not only our ecosystem, but also our economy. References: Costello, J.H. and Mianzan H.W.(2003).Sampling field distributions of  Mnemiopsis leidyi  JJJ  (Ctenophora, Lobata): planktonic or benthic method?  Journal of Plankton Research, 25(4),  JJJ   455-459. Greene, C.H., Landry, M.R., and Monger, C.R.(1986).Foraging Behavior and Prey Selection by  JJJ   the Ambush Entangling Predator Pleurobrachia bachei . Ecology, 67, 1493-1501. Hamer, H. H., Malzahn, A. M., and Boersma, M.(2011).The invasive ctenophore  Mnemiopsis  JJJ  leidyi:  a threat to fish recruitment in the North Sea?  Journal of Plankton Research, 33 , 137-  JJJ 144. Jaspers, C., Haraldsson, M., Lombard, F., Bolte, S. and Kiørboe, T. (2013).Seasonal dynamics of  JJ J  early life stages of invasive and native ctenophores give clues to invasion and bloom  JJJJ   potential in the Baltic Sea.   Journal of Plankton Research , 0(0), I-I3. Pechenik, J. (2009). Biology of the Invertebrates. 6th Ed. McGraw-Hill, USA
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