Investigating adaptation, competition and zonation of barnacles, Chthamalus stellatus (Poli) and Balanus balanoides (Linneas) on a semi-exposed southwestern seashore.

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Investigating adaptation, competition and zonation of barnacles, Chthamalus stellatus (Poli) and Balanus balanoides (Linneas) on a semi-exposed southwestern seashore.

Victoria Privett, Plymouth High School for Girls.

Introduction

Invasions of ecosystems by exotic species are increasing, especially in aquatic environments. Barnacles populate the coastlines of countries around the world. Specifically in Britain, we have two main types, which along the southwestern coastline have become distinguished for their different zones. Within this competition for feeding and survival, there is not substantial vertical overlap. This investigation is viable when talking about the competition of species. One of the most famous ecological field studies is that by Joseph Connell on the rocky shores of Scotland. The distribution of two competing species of barnacles, Balanus balanoides and Chthamalus stellatus, has shown to depend on physiology (tolerance of desiccation) and predation as well as aggressive competition by Balanus.

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Biology behind my investigation

As Chthamalus stellatus (Poli) has migrated to the British Isles, the competition between the native British barnacle, Balanus balanoides (Linneas) has become evididnt. There is clear zonation between the two species, with little overlay due to the diverse habitats at which the barnacles have become adapted. The main cause for this separation is due to the ability of the different species to survive under different conditions, to be able to function effectively, to feed and to reproduce successfully without hindrance from the environment around them. Things such a desiccation and the ability to feed are important for the species to productively colonise the rocky seashore and remain dominant. The competition between the two species resulted in Chthamalus migrating further up the shore. As being of southern origin, which is better adapted to heat and desiccation, the reasoning for this is that this species is then able to adapt to being in the exposed to sun and also not being submerged in water for great time periods like Balanus has.

Balanus balanoides

Chthamalus stellatus
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Desiccation

High sensitivity, no recoverability

Low Sensitivity, high recoverability

Temperature

High sensitivity, to extremes, especially heat

Not sensitive

Chthamalus is common or abundant over a few feet at the top of the midlittoral zone, whereas Balanus is abundant and dominant over the remaining midlittoral zone and littoral fringe. The ability to feed as well as reproduce is highly important as barnacles can only do so underwater. Chthamalus has shorter periods whilst in the water over long periods, whereas Balanus is covered with water for longer periods, with shorter periods of being exposed. ...

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