Spatio-temporal distribution and genetic characterization of some marine macroalgae of the Republic of Mauritius.

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Spatio-temporal distribution and genetic
characterization of some marine macroalgae of the
Republic of Mauritius.

• MPhil/PhD Research
• By Mrs Persand Jayshree
• (BSc Hons Biology with Environmental Sciences)
• SupervisorsDr Bhagooli Dr Taleb-Hossenkhan

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Studies on macroalgae distribution based on
morphological characteristics Dickie, 1875,
data collected during 1860sBoergesen 1940-1957,
data collected during late 1920s 1930s
Jagtap, 1993, data collected in 1987

• No DNA analyses done
• Relatively sparse data, dating back to 21 years,

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• Statement of problem
• Correct identification at molecular level
  absolute pre-requisite. Wrong identification ?
  misleading for research work
• Only short-term studies on species
  distribution and abundance reported

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Rationale of study

• Identification of macroalgae heavily reliant on
• cell detail
• and cell arrangement,
• gross morphology,
• Morphology of a single species vary in
  response to environmental conditions, for example
  low salinity and salinity shocks creating
  morphotypes.
• Molecular genetic tools ? to identify
  morphotypes.

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Morphotypes

• low salinity and salinity shocks can induce
  branching in Ulva intestinalis
• (U. intestinalis being unbranched) creating
  morphotypes similar to Ulva compressa.
• U. intestinalis and U. compressa are two
  distinct, genetically divergent and
  reproductively isolated species

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Rationale of study

• Mschigeni (1985) highlighted
• level of misidentification of specimens in
  some areas in the Indian Ocean may have an
  adverse effect on other studies and the
  commercial application of these specimens
• This study proposes a re-evaluation of
  macroalgae identification, abundance and
  distribution in the Mauritian lagoons and help
  identify possible effects on macroalage in our
  lagoons of the recent development that have
  occurred along the coastal shoreline in the
  recent years in Mauritius.

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Objectives of the study

• Monitor spatio-temporal changes in population
  dynamics of macroalgae 3
  consecutive years.
• Determine seasonal changes in wet weight and
  biomass of selected macroalage
• Genetically characterize different species of
  macroalgae using well-established molecular
  genetic protocols.
• Monitor the photo-physiological status of
  macroalgae over time in the field
• Measure physico-chemical parameters of water

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• Sites of study

Site Characteristics
Flic en Flac Possible water current that cause enough flushing of lagoon
Palmar/ Belle Mare Site of onion plantation along coast hence input of fertilizers through runoff
Trou aux biches Site of intense boating activities and freshwater seepage
Pointe aux Biches Site whereby there is drastic temperature fluctuations as macroalgae beds emerge out of water during low tides
Balaclava Undisturbed site (control) with low nutrients levels (AFRC, 2004)
Poste La Fayette Constant exchange of water (control) from off lagoon
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Jagtap (1993) documented

• 127 species of macroalgae
• confined to intertidal and lagoonal zones.
  
• 4 economically important genera
• Sargassum (9 species),
• Gracillaria, (4 species),
• Ulva (3 species)
• Enteromorpha (4 species).

very high commercial value worldwide and are
being harvested in millions of tonnes annualy
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Genetic characterisation

• Well-established genetic tools and markers ? to
  identify macroalgal species
• E.G.
• utility of rDNA internal transcribed spacer
  (ITS) sequences
• gene encoding the large subunit of RUBISCO, small
  subunit rDNA

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Methodology

• Genetic analysis of macroalgae
• Collection of preservation of selected species
• DNA Extraction
• PCR amplification of selected regions
• Purification of PCR products, cloning
  sequencing
• Comparison of sequences to those already present
  in DNA databases for identification purposes

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Photo-physiology of macroalgae

• Chl a fluorescence determined
  each season using Pulse Amplitude Modulated (PAM)
  fluorometer
• Measurement of
• minimum fluorescence (Fo)
• maximum fluorescence (Fm)
• maximum quantum yield of photosystem II (PSII)
  (Fv/Fm)
• photosynthetic electron transport rate (ETR)
• non-photochemical quenching (NPQ) at PSII
  derived from rapid light curves (RLCs)

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• Population dynamics cover
  density monitored
• (recording the time taken for algal
  re-colonization in cleared area)
• Specific growth rates of macroalgal species
  monitored
• length / mass 30-50
  individuals tagged (diameter and length)

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• Water Analysis
• 2/yr ? water samples to be collected for
  nitrate phosphates analyses ex situ
  (cadmium reduction method ascorbic acid method)
• water physico-chemical parameters including
  temperature, pH, salinity, turbidity dissolved
  oxygen monitored in situ
• Macroalgae distribution
• 4 equidistant transects perpendicular to
  shore evenly spaced macroalgae distribution and
  seasonal change monitored
• Wet weight 3 random samples in 25cm ? 25cm
  quadrat/transect
• Dry weight same samples dried at 800c

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• Expected output
• Macroalgae species distribution assessed on a
  spatio-temporal scales in the selected lagoons of
  Mauritius.
• Anthropogenic stressors v/s macroalgae
  species distribution/abundance
• suitability of certain macroalgae
  as bioindicators ???
• Verification of identity of morphologically
  characterized selected macroalgae using molecular
  genetic tools.
• Comparison of re-colonization success of specific
  macroalgae species in the different regions
  assessed

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Work carried out Primer Design

• Primers already designed for Ulva and Gracilaria
  genera for the purpose of genetic
  characterization
• DNA sequences corresponding to the 18S, ITS1,
  5.8S, ITS2, 28S rRNA genes and RuBisCo gene from
  Ulva and Gracilaria genera - retrieved from
  GenBank.
• DNA sequences belonging to several different
  species in each genus retrieved so that sequences
  could be compared and primers designed in the
  regions showing polymorphism only

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Figure 1 Organisation of one rDNA array. Single
repeat units (arrows) are tandemly organised.
Each of them consists of the rRNA genes 18S,
5.8S and 28S. Spacers separate these genes,
namely the external transcribed spacer (ETS), the
internal transcribed spacers (ITS 1 and ITS 2)
and the intergenic spacer (IGS).
http//webdoc.sub.gwdg.de/ebook/y/1999/whichmarke
r/index.htm
Multiple Sequence Alignments (MSAs) deriving from
different Ulva spp. and of the rubisco gene
cluster for Gracilaria spp. were then produced
using the MultAlin Software Primers, specific
for the amplification of the polymorphic regions,
were then designed using Primer3WWW software
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• Thank you
• for your consideration