ChAnge, Stress, Sustainability, and Aquatic ecosystem Resilience In
North African wetland lakes during the 20th century
The CASSARINA project highlighted the heavy human impacts on fragile
aquatic ecosystems and water resources in arid countries. Poor ecological
planning and lack of appropriate control of water-use projects are failing
to conserve water resources and the biodiversity they support.
The AIMS of the project were
1. To monitor water quality, zooplankton, phytoplankton, vegetation,
and fish diversity, growth rates, and pesticide content in 3 contrasting
lakes in each North African country.
2. To reconstruct changes over the last 100 years in the lakes' ecosystems
using multiproxy palaeolimnological methods. Proxies used from the sediment
records were diatoms, micro- and macro-invertebrates, plant macrofossils,
pollen, radionuclide dating, and sediment chemistry, including heavy
metals and persistent organic residues.
CASSARINA was an EU-INCO Project (1997-1999)
led by Roger Flower (University College London) and a team of scientists
from Morocco, Tunisia, Egypt, Norway, and UK.
Roger Flower University College London, UK
Mohammed Ramdani Institut Scientifique, Rabat, Morocco
Mejdeddine Kraïem Faculté des Sciences, Tunis University, Tunisia
Adel Fathi University of El Minia, Egypt
Hilary Birks Bergen University, Norway
Hani Abdelzaher University of El Minia,
Peter Appleby Liverpool University, UK
Cheddeli Ben Hamza Faculté des Sciences, Tunis University, Tunisia
John Birks Bergen University, Norway
Najat Elkhiati Faculté des Sciences, Casablanca, Morocco
Simon Patrick University College London, UK
Sylvia Peglar Bergen University, Norway
Andrew Peters Lancaster University, UK
Anne Bjune Bergen University, Norway
Ian Boomer Newcastle University, UK
Simon Dobinson University College London, UK
Sampling Lake Burullus
Sampling Megene Chitane
Of the 9 lakes, 3 were inland lakes, 1 had a remote connection to the
sea (Ichkeul), and 5 were lagoons.
Mean values of water chemistry variables for each CASSARINA lake and
minimum variance dendrogram that groups similar lakes. T.D.S. = total
All the nine lakes had undergone substantial ecosystem
changes during the last 100 years, at an increasing rate over recent
availability has generally decreased during the latter part of the
20th century at the Moroccan and Tunisian sites but the Nile Delta
sites have experienced a freshening trend during this period.
3 Nile Delta lakes used to have a natural balance between brackish
and more fresh-water conditions depending on the seasonal Nile flood.
The inflow of fresh water drained slowly, eventually allowing sea
water to penetrate once more. All have become fresher and more
due to year-round fresh-water input, increased agricultural fertilisation,
and increased human population since the early 20th century, accelerated
after the closure of the Aswan High Dam in 1964. All are being
reduced by land reclamation and are overgrown in varying degrees by water
Its salinity has been reduced by fresh-water overload from the Nile drains.
Fish quality is reduced by eutrophication and the spread of water hyacinth
and Azolla filiculoides on the water surface. Its size is being rapidly
reduced by land reclamation.
Changes in the biota of Lake Edku during the 20th century were recorded
from a core of the lake sediments. A saline phase with the marine foraminifer
Quinqueloculina seminulum, the bivalve Pholas dactylus, and the marine
plant Zostera was followed by less saline conditions as control of the
Nile flood and year-round fresh-water supply increased. Fresh-water molluscs
expanded in the 1940s and increased enormously after the closure of the
Aswan High Dam in 1964. Water weeds also increased, including indicators
of eutrophication such as Ceratophyllum (hornwort), Lemna (duckweed),
and Eichhornia (water hyacinth), and reedswamps grew up dominated by
Typha (cattail). Meanwhile, molluscs and foraminifera typical of brackish
lagoon conditions decreased as the water became fresher. Azolla nilotica thrived in the brackish and saline conditions early in the century, but
became extinct after about 1920 when nutrient levels began to increase.
Azolla filiculoides was introduced to the delta as a green fertilizer
(it fixes atmospheric nitrogen) and it spread across the lake in the
1990s. Occasional recent records of A. nilotica and Quinqueloculina are
probably reworked by fishermen's punt-poles.
a floating water fern, became extinct in the Nile Delta during the
last century. The latest record of megaspores in
lake sediments was from Lake Burullus at about 1965. (H.H. Birks (2003)
The recent extinction of Azolla nilotica in the Nile Delta, Egypt.
Acta Palaeobotanica 42, 203-213).
Nitella opaca oospores (right) of this macro-alga
were recorded in the sediments of Megene Chitane but living plants were
never found during
monitoring and it is assumed to be already extinct in this, its only
North African locality.
This huge shallow lake is suffering from land reclamation, industrial
and nutrient pollution, and overgrowth by water hyacinth (right). Formerly
saline or brackish, its salinity is reduced by year-round freshwater
inflow and poor drainage to the sea, and fis
h catches are reduced.
Extensive emergent reed beds, mainly of Phragmites, help to localise
pollution, but also prevent the circulation of saline water.
Lake Burullus retains some marine influence and is still mildly saline.
Fishermen using feluccas still make good fish catches.
Cores of lake sediment deposited over the last
century were taken from each lake to reconstruct palaeolimnological changes.The
published in volume 35 number 3-4 of Aquatic Ecology (2001). The following
articles are available electronically.
North African wetland lakes: characterization of nine
sites included in the CASSARINA Project
Palaeolimnological responses of nine North African lakes
in the CASSARINA Project to recent environmental changes and human impact
detected by plant macrofossil, pollen, and faunal analyses
Recent ecosystem dynamics in nine North African lakes
in the CASSARINA Project
Terrestrial pollen record of recent land-use changes
around nine North African lakes in the CASSARINA Project
Zooplankton (Cladocera, Ostracoda), Chironomidae and
other benthic faunal remains in sediment cores from nine North African
wetland lakes: the CASSARINA Project
Open water zooplankton communities in North African
wetland lakes: the CASSARINA Project
Radiometrically determined dates and sedimentation rates
for recent sediments in nine North African wetland lakes (the CASSARINA
UCL project write-up