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Spatio-temporal distribution and genetic characterization of some marine macroalgae of the Republic of Mauritius . PowerPoint Presentation
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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) Supervisors:Dr Bhagooli & Dr Taleb-Hossenkhan.

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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)

Supervisors:Dr Bhagooli & Dr Taleb-Hossenkhan

slide2

Studies on macroalgae distribution based on morphological characteristics: Dickie, 1875, data collected during 1860’sBoergesen 1940-1957, data collected during late 1920’s & 1930’s 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

rationale of study
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.

m orphotypes
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

rationale of study6
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.

objectives of the study
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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Site Characteristics

Sites of study

jagtap 1993 documented
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

genetic characterisation
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
methodology
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
photo physiology of macroalgae
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)

slide14
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
work carried out primer design
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/whichmarker/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