Difference between revisions of "Sandy shores"

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This article describes the habitat of the Sandy shores. It is one of the sub-categories within the section dealing with biodiversity of [[marine habitats and ecosystems]].
 
This article describes the habitat of the Sandy shores. It is one of the sub-categories within the section dealing with biodiversity of [[marine habitats and ecosystems]].
  
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Sandy beaches are soft shores that are formed by '''deposition''' of '''particles''' that have been carried '''by water currents''' from other areas. The transported material is in part derived from the erosion of shores, but the major part is derived from the land and transported by rivers to the sea. The two main types of beach material are '''quartz''' (=silica) sands of terrestrial origin and '''carbonate''' sands of marine origin. The carbonate sand is weathered from mollusk shells and skeletons of other animals. Other material includes heavy minerals, basalt (=volcanic origin) and feldspar.  
 
Sandy beaches are soft shores that are formed by '''deposition''' of '''particles''' that have been carried '''by water currents''' from other areas. The transported material is in part derived from the erosion of shores, but the major part is derived from the land and transported by rivers to the sea. The two main types of beach material are '''quartz''' (=silica) sands of terrestrial origin and '''carbonate''' sands of marine origin. The carbonate sand is weathered from mollusk shells and skeletons of other animals. Other material includes heavy minerals, basalt (=volcanic origin) and feldspar.  
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==Characteristics==
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The grain size of sand varies from very fine to very coarse. The particle diameter is shown in the table below.
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{| {{prettytable}} 
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! '''Generic Name'''
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! '''Particle Diameter (mm)'''
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|-
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| Very coarse
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| 1.0 to 2.0
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|-
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| Coarse
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| 0.50 to 2.0
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|-
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| Medium
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| 0.25 to 0.50
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|-
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| Fine
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| 0.125 to 0.50
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|-
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| Very Fine
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| 0.0625 to 0.125
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|-
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|}
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==Functioning and adaptations==
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The [[intertidal]] zone is covered part of the day by water and is part of the day exposed to air. High [[Tide|tides]] bring [[nutrients]] and food with it. When the [[tide]] retreats, waste products, eggs and larvae are taken. This causes changes for the organisms that live here. They have adapted to this changing environment, as seen on [[rocky shores]].
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==Biota==
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The distribution and abundance of the sediment infauna is mostly controlled by complex interactions between the physicochemical and biological properties of the sediment. <ref>Knox G.A. 2001. The ecology of seashores. CRC Press. p. 557</ref>
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The '''physicochemical''' properties are:
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* Grain size
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* Water content
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* Flushing rate of water through the sediment
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* Oxidation-reduction state
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* Dissolved oxygen
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* Temperature
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* Light
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* Organic content
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The '''biological''' properties are:
 +
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* Food availability and feeding activity
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* Reproductive effects on dispersal and settlement
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* Behavior that induces movement and aggregation
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* Intraspecific competition
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* Interspecific competition and competitive exclusion
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* Predation effects
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Most invertebrate phyla are represented on sandy beaches, either as interstitial forms or as members of the [[macrofauna]] <ref name="Brown and McLachlan"/>. The [[Macrofauna|macrofaunal]] forms are by far the better known. Some of them are typical of intertidal sands and their surf zone, while others are more characteristic of sheltered sandbanks, sandy muds or estuaries and are less common on open beaches of pure sand <ref name="Brown and McLachlan"/>.
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===[[Macrofauna|Macrofauna]]===
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[[Macrofauna]] of the sandy beaches are often abundant and, in some cases, attain exceptionally high densities. Their main  feature is the high degree of mobility displayed by all species. These animals may vary from a few mm to 20 cm in length.  The [[macrofauna]] community consists of those organisms too large to move between the sand grains. The [[macrofauna]] of  sandy beaches includes most major invertebrate taxa although it has been recognised that molluscs, [[crustacea|crustaceans]] and  polychaetes are the most important. There is a tendency for [[crustacea|crustaceans]] to be more abundant on tropical sandy beaches or  more exposed beaches and molluscs to be more abundant on less exposed and on temperate beaches although there are  many exceptions of this and polychaetes are sometimes more abundant than either of these taxa. Generally [[crustacea|crustaceans]] dominate the sands towards the upper tidal level and molluscs the lower down level <ref name="Brown and McLachlan">Brown & McLachlan 1990</ref>. Physical factors,  primary wave action and particle size of the sand largely determine distribution and diversity of the invertebrate [[macrofauna]] of sandy beaches. Food input and surf-zone productivity may determinate the abundance population. Water  movement is important parameter controlling [[Macrofauna|macrofaunal]] distribution on beaches.
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===[[Meiofauna]]===
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In contrast to the wave-swept surface sand inhabited by most of the [[macrofauna]], the interstitial system is truly three-dimensional, often having great vertical extent in the sand. The porous system averages about 40% of the total sediment volume. Its inhabitants include small metazoans forming the [[meiofauna]], protozoans, bacteria and diatoms<ref name="Brown and McLachlan"/>. The [[meiofauna]] is defined as those metazoan animals passing undamaged though 0.5 to 1.0 mm sieves and trapped on 30 mm screens. On most beaches the interstitial fauna is rich and diverse, even exceeding the [[macrofauna]] in [[biomass]] in some cases<ref name="Brown and McLachlan"/>. The dominant taxa of sandy beach [[meiofauna]] are nematodes and harpacticoid copepod with other important groups including turbellarians, oligochaetes, gastrotrichs, ostracods and tardigdades.
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===Insects===
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Terrestrial insects and vertebrates are frequently ignored in accounts of sandy beaches. These animals are usually a conspicuous component of the [[ecosystems|ecosystem]], often rivalling the aquatic [[macrofauna]] in terms of [[biomass]] and having a significant impact on the system with regard to predation and scavenging.
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|AuthorFullName=TÖPKE, Katrien
 
|AuthorFullName=TÖPKE, Katrien
 
|AuthorName=Ktopke}}
 
|AuthorName=Ktopke}}
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{{author
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|AuthorID=5254
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|AuthorName= Lechu
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|AuthorFullName= Kotwicki, Lech}}
  
 
[[Category:Marine habitats and ecosystems]]
 
[[Category:Marine habitats and ecosystems]]

Revision as of 10:10, 25 July 2008

This article describes the habitat of the Sandy shores. It is one of the sub-categories within the section dealing with biodiversity of marine habitats and ecosystems.


Introduction

Sandy shores or beaches are loose deposits of sand, gravel or shells that cover the shoreline in many places. They make up two-thirds of the world’s ice-free coastlines. Beaches serve as buffer zones or shock absorbers that protect the coastline, sea cliffs or dunes from direct wave attack. It is an extremely dynamic environment where sand, water and air are always in motion. Beaches also provide important coastal recreational areas for a many people. Fine-grained sand beaches tend to be quite flat.


Sandy beach in Middelkerke - Belgium [1]


Formation

Sandy beaches are soft shores that are formed by deposition of particles that have been carried by water currents from other areas. The transported material is in part derived from the erosion of shores, but the major part is derived from the land and transported by rivers to the sea. The two main types of beach material are quartz (=silica) sands of terrestrial origin and carbonate sands of marine origin. The carbonate sand is weathered from mollusk shells and skeletons of other animals. Other material includes heavy minerals, basalt (=volcanic origin) and feldspar.


Characteristics

The grain size of sand varies from very fine to very coarse. The particle diameter is shown in the table below.

Generic Name Particle Diameter (mm)
Very coarse 1.0 to 2.0
Coarse 0.50 to 2.0
Medium 0.25 to 0.50
Fine 0.125 to 0.50
Very Fine 0.0625 to 0.125


Functioning and adaptations

The intertidal zone is covered part of the day by water and is part of the day exposed to air. High tides bring nutrients and food with it. When the tide retreats, waste products, eggs and larvae are taken. This causes changes for the organisms that live here. They have adapted to this changing environment, as seen on rocky shores.


Biota

The distribution and abundance of the sediment infauna is mostly controlled by complex interactions between the physicochemical and biological properties of the sediment. [2]

The physicochemical properties are:

  • Grain size
  • Water content
  • Flushing rate of water through the sediment
  • Oxidation-reduction state
  • Dissolved oxygen
  • Temperature
  • Light
  • Organic content


The biological properties are:

  • Food availability and feeding activity
  • Reproductive effects on dispersal and settlement
  • Behavior that induces movement and aggregation
  • Intraspecific competition
  • Interspecific competition and competitive exclusion
  • Predation effects


Most invertebrate phyla are represented on sandy beaches, either as interstitial forms or as members of the macrofauna [3]. The macrofaunal forms are by far the better known. Some of them are typical of intertidal sands and their surf zone, while others are more characteristic of sheltered sandbanks, sandy muds or estuaries and are less common on open beaches of pure sand [3].


Macrofauna

Macrofauna of the sandy beaches are often abundant and, in some cases, attain exceptionally high densities. Their main feature is the high degree of mobility displayed by all species. These animals may vary from a few mm to 20 cm in length. The macrofauna community consists of those organisms too large to move between the sand grains. The macrofauna of sandy beaches includes most major invertebrate taxa although it has been recognised that molluscs, crustaceans and polychaetes are the most important. There is a tendency for crustaceans to be more abundant on tropical sandy beaches or more exposed beaches and molluscs to be more abundant on less exposed and on temperate beaches although there are many exceptions of this and polychaetes are sometimes more abundant than either of these taxa. Generally crustaceans dominate the sands towards the upper tidal level and molluscs the lower down level [3]. Physical factors, primary wave action and particle size of the sand largely determine distribution and diversity of the invertebrate macrofauna of sandy beaches. Food input and surf-zone productivity may determinate the abundance population. Water movement is important parameter controlling macrofaunal distribution on beaches.


Meiofauna

In contrast to the wave-swept surface sand inhabited by most of the macrofauna, the interstitial system is truly three-dimensional, often having great vertical extent in the sand. The porous system averages about 40% of the total sediment volume. Its inhabitants include small metazoans forming the meiofauna, protozoans, bacteria and diatoms[3]. The meiofauna is defined as those metazoan animals passing undamaged though 0.5 to 1.0 mm sieves and trapped on 30 mm screens. On most beaches the interstitial fauna is rich and diverse, even exceeding the macrofauna in biomass in some cases[3]. The dominant taxa of sandy beach meiofauna are nematodes and harpacticoid copepod with other important groups including turbellarians, oligochaetes, gastrotrichs, ostracods and tardigdades.


Insects

Terrestrial insects and vertebrates are frequently ignored in accounts of sandy beaches. These animals are usually a conspicuous component of the ecosystem, often rivalling the aquatic macrofauna in terms of biomass and having a significant impact on the system with regard to predation and scavenging.














The main author of this article is TÖPKE, Katrien
Please note that others may also have edited the contents of this article.
Citation: TÖPKE, Katrien (2008): Sandy shores. Available from http://www.coastalwiki.org/wiki/Sandy_shores [accessed on 24-11-2024]


The main author of this article is Kotwicki, Lech
Please note that others may also have edited the contents of this article.
Citation: Kotwicki, Lech (2008): Sandy shores. Available from http://www.coastalwiki.org/wiki/Sandy_shores [accessed on 24-11-2024]
  1. ↑ http://commons.wikimedia.org/wiki/Image:2005-06-26-Middelkerke-55.jpg
  2. ↑ Knox G.A. 2001. The ecology of seashores. CRC Press. p. 557
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Brown & McLachlan 1990
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