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<?xml version="1.0" encoding="utf-8" ?><!DOCTYPE article PUBLIC "-//Atypon//DTD Atypon Systems Journal Archiving and Interchange NLM DTD v3.0.0 20090430//EN" "atypon-archivearticle3.dtd">
<article xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mml="http://www.w3.org/1998/Math/MathML" article-type="research-article">
<front>
<journal-meta>
<journal-id journal-id-type="pmc">connect</journal-id>
<journal-id journal-id-type="publisher-id">connect</journal-id>
<journal-title-group>
<journal-title>QScience Connect</journal-title>
</journal-title-group>
<issn pub-type="ppub">2223-506X</issn>
<publisher>
<publisher-name>Bloomsbury Qatar Foundation Journals</publisher-name> </publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="publisher-id">3</article-id>
<article-id pub-id-type="doi">10.5339/connect.2011.3</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Research
article</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>Distribution of non-marine diatoms in surface sediments of streams in Socotra Island, Yemen</article-title>
<trans-title-group xml:lang="AR">
<trans-title>توزيع الدياتومات الغير بحرية في الرواسب السطحية الحديثة في بعض وديان جزيرة
سقطرى –
</trans-title>
</trans-title-group>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<string-name>
<given-names>Abdelfattah A.</given-names>
<x> </x>
<surname>Zalat</surname> </string-name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<x><sup>,</sup></x> <xref ref-type="fn" rid="FN3"><sup>3</sup></xref>
<x> and </x></contrib>
<contrib contrib-type="author">
<string-name>
<given-names>Mohammed
A.</given-names>
<x> </x>
<surname>Al-Wosabi</surname> </string-name>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<x><sup>,</sup></x>
<xref ref-type="corresp" rid="c1"><sup>⁎</sup></xref>
<x> </x></contrib>
<aff id="aff1"><sup>1</sup>Hodiedah University, Faculty of
Marine and Environmental Science, Marine Geology Department, Hodeidah,
Yemen</aff>
<aff id="aff2"><sup>2</sup>Sana’a University, Faculty of Science, Earth and Environmental Sciences
Department, Sana’a, Yemen <!--\newline ~\\[-5pt]--></aff></contrib-group>
<author-notes>
<corresp id="c1"><sup>⁎</sup>Corresponding author. Tel.: 00967 777650710. E-mail: ma_wosabi@yahoo.com</corresp>
<fn id="FN3">
<label><sup>3</sup></label>
<p>E-mail: abzalat@yahoo.com</p></fn>
<fn id="FN4">
<label>Academic Editor: </label>
<p>Dr. Habib Alimohammadian,
Geological Survey of Iran, Iran</p></fn>
</author-notes>
<pub-date pub-type="pub">
<day>18</day>
<month>11</month>
<year>2011</year> </pub-date>
<issue content-type="issue-sequence">2011</issue>
<elocation-id>3</elocation-id>
<history>
<date date-type="received">
<day>29</day>
<month>6</month>
<year>2011</year></date>
<date date-type="accepted">
<day>06</day>
<month>10</month>
<year>2011</year></date></history>
<permissions>
<copyright-statement>© 2011 Zalat & Al-Wosabi, licensee Bloomsbury Qatar Foundation
Journals. This is an open access article distributed under the terms of the
Creative Commons Attribution License CC BY 3.0 which permits unrestricted
use, distribution and reproduction in any medium, provided the original
work is properly cited.</copyright-statement>
<copyright-year>2011</copyright-year>
<copyright-holder>Bloomsbury Qatar Foundation Journals</copyright-holder> </permissions>
<self-uri content-type="pdf" xlink:href="connect.2011.3.pdf" xmlns:xlink="http://www.w3.org/1999/xlink"/>
<abstract>
<title>Abstract</title>
<p>Abundance and species composition of non-marine benthic diatom assemblages were studied from surface sediments samples of 11 streams distributed in Socotra Island, located in the northwest Indian Ocean. A total of 145 diatom species, representing 44 genera, were identified. The overall diatom communities appear to be the first recorded off the island. Pennales and non-planktonic taxa were most dominant over centrales and planktonic forms, both in diversity of genera and species. The majority of recognized diatoms are of cosmopolitan distribution. The predominant diatom flora in the surface sediment samples follow:
<italic>Synedra ulna, Synedra longissima, Encyonema caespitosum, Encyonema silesiacum, Encyonemopsis microcephala, Mastogloia braunii, Mastogloia dansei, Mastogloia elliptica, Navicula cryptocephala, Navicula cryptotenella, Navicula rhynchocephala, Navicula cincta, Nitzschia amphibian, Nitzschia frustulum, Nitzschia perminuta, Cocconeis placentula, Pleurosira laevis and Staurosirella pinnata</italic>. These are found in addition to the common occurrence of
<italic>Amphora coffeaeformis, Amphora Montana, Anomoeoneis sphaerophora, Cyclotella meneghiniana, Cymbella affinis, Diploneis elliptica, Encyonema mesianum, Diploneis smithii, Gomphonema gracile, Gomphonema parvulum, Kobayasia subtilissima, Mastogloia smithii, Navicula minuscule, Navicula notha, Navicula tenelloides, Nitzschia obtuse, Nitzschia palea, Nitzschia scalaris, Synedra nana, Tryblionella acuminate, Tryblionella granulate</italic> and
<italic>Tryblionella punctata</italic>. Multivariate statistical techniques including detrended correspondence and cluster analyses were used to summarize changes in the diatom assemblages present in the examined streams. The results indicated six major diatom assemblages with a variation in dominant species. Each assemblage reflects distinctive environmental conditions based on salinity preference of the recognized and dominant.</p></abstract>
<trans-abstract xml:lang="AR"><title>الملخّص</title>
<p>
تعتبر هذه الدراسة هي الأولى من نوعها على رسوبيات جزيرة سقطرى والتي تم فيها دراسة تواجد وتركيب الدياتومات التي تم استخلاصها من الرسوبيات السطحية الحديثة والتي جمعت من 11 واديا مائيا في جزيرة سقطرى الواقعة في الجزء الشمالي الغربي للمحيط الهندي. أمكن تعريف 145 نوعا من الدياتومات التي تنتمي إلى 44 جنسا.
</p>
<p>
إن الأنواع التي تم تعريفها تمثل فيها الدياتومات القاعية الريشية أكثر من الدياتومات المركزية الطافية، وتعتبر تلك الأنواع من الأنواع ذات التوزيع العالمي. كان هناك تفاوت في نسبة تواجد الأنواع بشكل ملحوظ ولكن كانت الأنواع الأكثر وفرة هي:
</p>
<p>
Synedra ulna, Synedra longissima, Encyonema caespitosum, Encyonema silesiacum, Encyonemopsis microcephala, Mastogloia braunii, Mastogloia dansei, Mastogloia elliptica, Navicula cryptocephala. Navicula cryptotenella, Navicula rhynchocephala, Navicula cincta, Nitzschia amphibian, Nitzschia frustulum, Nitzschia perminuta, Cocconeis placentula, Pleurosira laevis, Staurosirella pinnata.
</p>
<p>
أما الأنواع المسجلة بأعداد شائعة فهي:
</p>
<p>
Amphora coffeaeformis, Amphora Montana, Anomoeoneis sphaerophora, Cyclotella meneghiniana, Cymbella affinis, Diploneis elliptica, Encyonema mesianum, Diploneis smithii, Gomphonema gracile, Gomphonema parvulum, Kobayasia subtilissima, Mastogloia smithii, Navicula minuscule, Navicula notha, Navicula tenelloides, Nitzschia obtuse, Nitzschia palea, Nitzschia scalaris, Synedra nana, Tryblionella acuminate, Tryblionella granulate and Tryblionella punctata.
</p>
<p>
أظهرت نتائج التطبيقات الإحصائية على المتغيرات المتماثلة والتحاليل العنقودية والتي استخدمت لاستخلاص التغيرات في مجاميع الدياتومات التي تم تعريفها وجود ست مجاميع من الدياتومات بناء على ماعكسته متغيرات ببيئية محددة وبالذات متغير الملوحة.
</p>
</trans-abstract>
<kwd-group kwd-group-type="author">
<title>Keywords</title>
<kwd>diatoms</kwd>
<x>, </x>
<kwd>multivariate analysis</kwd>
<x>, </x>
<kwd>streams</kwd>
<x>, </x>
<kwd>Socotra</kwd>
<x>, </x>
<kwd>Yemen</kwd></kwd-group>
</article-meta>
</front>
<body>
<sec>
<title>Introduction</title>
<p>Streams are among the most threatened habitat types in the recent times. Awareness
of the deleterious effects of human pressures on streams has resulted in a long history
of monitoring using many biological indicators <xref ref-type="bibr" rid="b1 b2 b3">[1–3]</xref> A
number of studies have evaluated the effects of different stressors on stream
assemblages and many assessment systems have been developed including one or
more taxonomic groups. Diatoms are the most common and diverse group of algae
in many rivers and streams, and thus are important components of these
ecosystems <xref ref-type="bibr" rid="b4">[4]</xref>. They are considered more suitable for biological
monitoring than many other organisms because of their seeming ubiquity,
short generation time, sensitivity to changes in nutrient levels, and diverse
assemblages <xref ref-type="bibr" rid="b5">[5]</xref>. Moreover, diatoms are often used to monitor the
environmental changes in rivers and streams because of their range of response to
ionic content and composition. Their use in monitoring would be enhanced
significantly if species responses to the concentration of major ions in fresh waters
were better quantified <xref ref-type="bibr" rid="b6">[6]</xref>.</p>
<p>In North America, Europe, Australia and Africa, benthic diatoms are frequently used to
assess the integrity of stream ecosystems <xref ref-type="bibr" rid="b7 b8 b9 b10 b11 b12">[7–12]</xref>.
Moreover, several studies have addressed the tolerances and preferences of diatoms along
a number of environmental gradients such as salinity, pH, trophy, saprobity and current
preference <xref ref-type="bibr" rid="b13 b14 b15 b16">[13–16]</xref>. Benthic diatoms are often used for
assessing nutrient enrichment <xref ref-type="bibr" rid="b17 b16 b18 b19">[17,16,18,19]</xref>,
salinity <xref ref-type="bibr" rid="b20">[20]</xref> and acidity <xref ref-type="bibr" rid="b21 b22 b23">[21–23]</xref>. They
also give a quick response to environmental changes <xref ref-type="bibr" rid="b24 b25
b26 b27 b28 b29 b30 b31 b32 b33 b34">[24–34]</xref>. In addition, they are now
increasingly used to examine changes to river systems <xref ref-type="bibr" rid="b35
b36">[35,36]</xref>.</p>
<p>The present study focuses on distribution of diatoms in some streams from Socotra
Island at north-western of Indian Ocean. This island is considered one of the most
fascinating places on earth. It has very rich and diverse animals and plants, which are
found nowhere else on the earth. Many fauna and flora groups in the island remain to
be discovered. Socotra Island has drawn the attention of many researchers in recent
times <xref ref-type="bibr" rid="b37 b38 b39 b40 b41 b42 b43 b44 b45 b46">[37–46]</xref>. Their
studies mainly dealt with the biology, geochemistry, ecology, biodiversity, fisheries
and climate of the island. Relatively a few geological studies were carried out on
this island due to its extremely isolated location. However, no research on
diatom communities from Socotra Island has been carried out. In addition,
stream diatom autecology and distribution patterns within the island remain
unknown.</p>
<p>The main objective of this study was to obtain preliminary data about the
composition of the non-marine benthic diatom flora and their distribution in
different eleven streams in Socotra Island. This data can be used as the
biodiversity database that will be benefit for monitoring of the environmental
change.</p>
</sec>
<sec>
<title>Island description</title>
<p>The Socotra is the largest Yemeni island, located at the northwest Indian Ocean, between the latitudes <!--\xdollar\rm -->12<sup>∘</sup>30<!--\xdollar-->’N and the
longitudes <!--\xdollar\rm --> 54<sup>∘</sup> E<!--\xdollar-->.
The island covers an area of about 3650 km<sup>2</sup> and it has about 500 km of coastal line
and is more than 130 km long from east to west, and 40 km wide from north
to south, with a spine of spectacular 1,500 m mountains along its length
(<xref rid="fig1">Fig. 1</xref>). To the north lies Oligocene-Miocene oceanic crust in water depth
reaching in excess of 2500m; whilst south of the island depth is generally less
than 250m over a distance of 70 km (Laughton, 1966 and Laughton et al.
1970).
<fig id="fig1">
<label>Figure. 1</label> <!--,aboveskip=.8pc,abovecapskip=-.5pc,belowskip=-.5pc--><caption>
<title> Map of Socotra Island, showing the location of sampling sites at 11
streams.</title>
</caption>
<graphic xlink:href="gr1.jpg" xmlns:xlink="http://www.w3.org/1999/xlink"/>
</fig>
<!--\setFloat [b!]{fig1}--></p>
<p>The topographic elements in Socotra Island are: (1) The range of Hajar Mountains,
which are located at the eastern part of the island along Arida Bay, and extending
north east to south west at a distance of about 25 km. (2) The central plateau, which
occupies most of the island area. (3) Coastal plains, which are situated in the north
and south of the island. (4) The wadis (valleys): The plains are interspersed by
many valleys that run in the northern and southern parts of the island. The
wadis are represented by small streams. Many of the north-flowing wadis
terminate in small fresh or brackish lakes separated from the sea by spits an
admixture of fine grey soil. Tectonically, the Socotran Platform was affected
by the three phases of extensional tectonics associated with the episodic
movement of the Arabian, African and Indian Plates. These are 1: Late
Jurassic to Early Cretaceous extension associated with the breakup of eastern
Gondwanaland; 2: Late Jurassic to Early Cretaceous extension associated with
failed rifting along the Arabian Peninsula Najd Trend (several phases of
subsequent structuring, with characteristic translational aspects to the tectonic
movement, occurred in the Late Cretaceous/Early Palaeocene and Early
Oligocene); and 3: Oligi-Miocene extention related to the rifting of the Gulf of
Aden <xref ref-type="bibr" rid="b47">[47]</xref>.</p>
<p>Climatically, the island lies in the northern tropics (<!--\xdollar\rm -->12<sup>∘</sup>30<!--\xdollar-->’N–<!--\xdollar\rm -->54<sup>∘</sup>E<!--\xdollar-->)
of the northwest Indian Ocean and is strongly influenced by the East
African–Indian monsoon <xref ref-type="bibr" rid="b37 b38 b45">[37,38,45]</xref>. In general,
the island is prevailed generally with relatively hot weather of which
the average daily temperature in Hajar Mountains ranges between 25–<!--\xdollar\rm -->28<sup>∘</sup>C<!--\xdollar-->. In
June and July however, the temperatures reach its extreme and fall during January
and February. The average humidity ratio ranges between max 55% in August
and min 7% in January. The island is subjected to sharp southern westerly
winds during the summer months (June, July, August) with an average speed
between 13–18 km/h, whose speed decreases gradually during September till
they end at the beginning of October. The average annual rainfall of the
island is 150 mm on the coastal plain to upwards of 500 mm in the interior
mountains <xref ref-type="bibr" rid="b48">[48]</xref>, but this quantity fluctuates to a great extent from
one year to another.</p>
</sec>
<sec>
<title>Materials and methods</title>
<p>Over the course of this study, eleven streams draining into the north and north
eastern side of Socotra Island were sampled between 14 and 28 July, 2008
(<xref rid="fig1">Fig. 1</xref> and
<xref rid="tbl1">Table 1</xref>). The streams are small second or third order systems no more than
4–10m wide and less than 1m deep. They were clear and shallow (max. depth
15–70 cm) (<xref rid="fig2">Fig. 2</xref>). Stream water specific conductance was generally low (20–250 <!--\xdollar\rm --><!--\TexTMu\removeaccent{-->μ<!--}-->S/cm<!--\xdollar-->), with
higher values potentially representing close to the coast. The stream water pH was
alkaline (7.3–8.4) with no clear altitudinal trend.
<table-wrap id="tbl1">
<label>Table 1</label>
<caption>
<title> The locations of the studied samples in Socotra Island.</title>
</caption>
<table frame="hsides" rules="groups">
<colgroup>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/></colgroup>
<thead>
<tr valign="top">
<td align="left">Sample No. </td>
<td align="left">Location </td>
<td align="left">Latitude ‘N’ </td>
<td align="left">Longitude ‘E’ </td>
</tr></thead>
<tbody>
<tr valign="top">
<td align="left">1 </td>
<td align="left">Arer stream (fresh water) </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 33<!--^{-->′<!--}--> 09<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 27<!--^{-->′<!--}--> 34<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">2 </td>
<td align="left">From the mouth of the Arer stream </td>
<td align="left"> </td>
<td align="left"> </td>
</tr>
<tr valign="top">
<td align="left">3 </td>
<td align="left">Terbek area (stream) </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 34<!--^{-->′<!--}--> 53<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 23<!--^{-->′<!--}--> 44<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">4 </td>
<td align="left">Wadi Shafa </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 36<!--^{-->′<!--}--> 19<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 19<!--^{-->′<!--}--> 18<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">5 </td>
<td align="left">Wadi Qariat Tawmer </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 38<!--^{-->′<!--}--> 48<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 13<!--^{-->′<!--}--> 19<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">6 </td>
<td align="left">Wadi Qariat Tawmer </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 39<!--^{-->′<!--}--> 11<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 12<!--^{-->′<!--}--> 36<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">7 </td>
<td align="left">Wadi Debni </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 38<!--^{-->′<!--}--> 52<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 08<!--^{-->′<!--}--> 32<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">8 </td>
<td align="left">Wadi Delshieh </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 41<!--^{-->′<!--}--> 24<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 07<!--^{-->′<!--}--> 48<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">9 </td>
<td align="left">Wadi Souq </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 40<!--^{-->′<!--}--> 04<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 03<!--^{-->′<!--}--> 43<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">10 </td>
<td align="left">Wadi Serhen </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 38<!--^{-->′<!--}--> 42<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 02<!--^{-->′<!--}--> 11<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">11 </td>
<td align="left">Wadi Serhen </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 38<!--^{-->′<!--}--> 44<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 02<!--^{-->′<!--}--> 20<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">12 </td>
<td align="left">Wadi Hadibo </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 38<!--^{-->′<!--}--> 51<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 54<sup>∘</sup> 01<!--^{-->′<!--}--> 39<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">13 </td>
<td align="left">Wadi Noujahar </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 38<!--^{-->′<!--}--> 19<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 53<sup>∘</sup> 56<!--^{-->′<!--}--> 16<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">14 </td>
<td align="left">Wadi Serhen (Dexem) </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 29<!--^{-->′<!--}--> 41<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 53<sup>∘</sup> 59<!--^{-->′<!--}--> 29<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
<tr valign="top">
<td align="left">15 </td>
<td align="left">Dhahadhhah (fresh water) </td>
<td align="left"><!--\xdollar\rm --> 12<sup>∘</sup> 30<!--^{-->′<!--}--> 40<!--^{-->″<!--}--><!--\xdollar--> </td>
<td align="left"><!--\xdollar\rm --> 53<sup>∘</sup> 27<!--^{-->′<!--}--> 00<!--^{-->″<!--}--><!--\xdollar--> </td>
</tr>
</tbody>
</table>
</table-wrap>
<!--\setFloat [pos=b]{tbl1}--></p>
<p>Diatoms were extracted from 20g of dry sediments of each sample. The
sample was first treated by 30% HCl with heating to boiling point in order
to remove any carbonate fraction. Each sample was rinsed by distilled
water several times to become neutral. The procedure was repeated with <!--\xdollar\rm -->H
<sub>2</sub>O
<sub>2</sub><!--\xdollar-->to eliminate the organic matter, and the sample was then rinsed and
decanted repeatedly in distilled water. The coarse particles were removed
by further decantation. Finally, one drop of the final suspension was
dried onto cover slips, then mounted onto slides using Canada Balsam<sup><!--\text{-->®<!--}--></sup>(<!--\xdollar\rm -->R.I=1.74<!--\xdollar-->) for
light microscopy investigations. 500 diatom valves were counted and identified in each
sample at 1000x magnification with Carl Zeiss microscope.</p>
<p>Nomenclature and identification of diatoms were made using <xref ref-type="bibr" rid="b49
b50 b51 b52 b53 b54 b55 b56">[49–56]</xref>. In the case of recently described or redefined
taxa, more recent literature was applied <xref ref-type="bibr" rid="b57 b58 b59 b60 b61 b62
b63 b64 b65 b66 b67">[57–67]</xref>. All identifications were to species level where possible
and the relative abundance values were calculated. The most dominant species that
have relative abundance over 5% of the total diatom valves in 15 examined samples
were analyzed using the multivariate statistical programs. One barren sample is
excluded from the analysis. Examination of community patterns within the dataset
was done primarily using detrended correspondence analysis (DCA). Cluster analysis
was carried out using Euclidean distance measure and the average clustering method
of the investigated sampling sites <xref ref-type="bibr" rid="b68">[68]</xref> to distinguish the diatom
assemblages.</p>
</sec>
<sec>
<title>Diatom results</title>
<p>A total of 145 specific and infraspecific diatom taxa representing 44 genera were
observed in all examined streams. A list of all taxa encountered is presented
in
<xref rid="tbl2">Table 2</xref>. All of the recognized diatom flora are reported for the first time for the
island. The distribution pattern of the identified diatom communities varies
significantly between the studied sites and indicates changes in the floristic
composition. At least 45 genera and 142 species of pennate diatoms and at least three
genera with five species of centric diatoms were identified. The most dominant
diatom flora in the streams were cosmopolitan. The highest and lowest numbers of
species were reported at the site 14 (Wadi Serhen) and site 12 (Wadi Hadibo)
respectively. The species composition was very variable from stream to other. The
dominant species most commonly found in every stream were
<italic>Synedra ulna</italic> and
<italic>Nitzschia frustulum</italic>. In the Wadi Serhen and Wadi Shafa streams, the diatom flora
were most dominant than the others streams, and the species composition was
differed considerably.
<table-wrap id="tbl2">
<label>Table 2</label>
<caption>
<title> List of the identified diatoms in the studied streams sites. (A <!--\xdollar\rm -->=<!--\xdollar--> abundant, C <!--\xdollar\rm -->=<!--\xdollar--> common, F <!--\xdollar\rm -->=<!--\xdollar--> frequent, R <!--\xdollar\rm -->=<!--\xdollar--> rare, X <!--\xdollar\rm -->=<!--\xdollar--> excellent, G <!--\xdollar\rm -->=<!--\xdollar--> good, M <!--\xdollar\rm -->=<!--\xdollar--> medium, and P <!--\xdollar\rm -->=<!--\xdollar--> poor)</title>
</caption>
<table frame="hsides" rules="groups">
<colgroup>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/></colgroup>
<thead>
<tr valign="top">
<td align="left">Diatom flora </td>
<td align="left">Sampling Sites </td>
<td align="left">1 </td>
<td align="left">2 </td>
<td align="left">3 </td>
<td align="left">4 </td>
<td align="left">5 </td>
<td align="left">6 </td>
<td align="left">7 </td>
<td align="left">8 </td>
<td align="left">9 </td>
<td align="left">10 </td>
<td align="left">11 </td>
<td align="left">12 </td>
<td align="left">13 </td>
<td align="left">14 </td>
<td align="left">15 </td>
</tr>
<tr valign="top">
<td align="left"> </td>
<td align="left">Abundance </td>
<td align="left">F </td>
<td align="left">F </td>
<td align="left">F </td>
<td align="left">A </td>
<td align="left">C </td>
<td align="left">F </td>
<td align="left">A </td>
<td align="left">C </td>
<td align="left">A </td>
<td align="left">F </td>
<td align="left">C </td>
<td align="left">R </td>
<td align="left">B </td>
<td align="left">A </td>
<td align="left">A </td>
</tr>
<tr valign="top">
<td align="left"> </td>
<td align="left">Preservation </td>
<td align="left">M </td>
<td align="left">M </td>
<td align="left">P </td>
<td align="left">G </td>
<td align="left">M </td>
<td align="left">M </td>
<td align="left">G </td>
<td align="left">M </td>
<td align="left">G </td>
<td align="left">M </td>
<td align="left">P </td>
<td align="left">M </td>
<td align="left">X </td>
<td align="left">M </td>
<td align="left">G </td>
</tr></thead>
<tbody>
<tr valign="top">
<td colspan="2" align="left">
<italic>Achnanthes brevipes intermedia</italic> (Kütz.) Cleve. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Achnanthidium exiguum</italic> (Grunow) Czarn. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Achnanthidium exilis</italic> (Kütz.) Round & Bukht. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Achnanthidium lanceolatum</italic> Breb. ex Kütz. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Achnanthidium microcephalum Kütz</italic>. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Achnanthidium minutissimum</italic> (Kütz.) Czarn. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Amphora angusta</italic> Greg. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">F </td>
<td align="left">R </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Amphora coffeaeformis</italic> (C.Agardh) Kütz. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">F </td>
<td align="left">F </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">F </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left">F </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Amphora commutata</italic> Grun. in Van Heurck. </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left">F </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Amphora cymbifera</italic> Greg. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">F </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Amphora holsatica.</italic> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left">F </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Amphora montana</italic> Krasske. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">F </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left">R </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">F </td>
<td align="left">F </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Amphora normanii Rabenh</italic>. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left">F </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Amphora ovalis (</italic>Kütz.) Kütz. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left"> </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Amphora sp.</italic> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">F </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Amphora veneta Kütz</italic>. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">F </td>
<td align="left">F </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
</tr>
<tr valign="top">
<td colspan="2" align="left">
<italic>Anomoeoneis sphaerophora</italic> (Ehrenb.) Pfitz. </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left"> </td>
<td align="left">R </td>
<td align="left"> </td>
<td align="left"> </td>
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<td align="left">F </td>
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<italic>Brachysira vitrea</italic> (Grun.) R. Ross in Hartley. </td>
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<td align="left">F </td>
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<italic>Caloneis budensis</italic> (Grunow) Krammer. </td>
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<italic>Campylodiscus bicostatus</italic> W. Smith in Roper. </td>
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<italic>Cocconeis disculoides</italic> Hust. </td>
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<italic>Cocconeis placentula</italic> Ehrenb. </td>
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<italic>Cocconeis pseudomarginata</italic> Greg. </td>
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<italic>Cocconeis scutellum</italic> Ehrenb. </td>
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<italic>Cocconeis speciosa</italic> Greg. </td>
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<italic>Cocconeis</italic> sp. </td>
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<td align="left">R </td>
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<italic>Cocconeis thumensis</italic> A. Mayer. </td>
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