Tuesday, December 27, 2011

Survey of Peddapalem-Ponnapudi (Lakshmipuram, Kottur) Mangrove Wetlands



Sonneratia apetala: Tree & Fruits


Conversion of mangrove wetlands into salt pans
Excoecaria agallocha

<-- Mangroves felled & transported


Furthering my study of mangroves of Nellore district, I undertook a field visit to the Iskapalle lagoon in Vidavalur mandal. Here I found a very vast wetland occupied by mangroves. In this lagoon a fresh water body, Pyderu stream joins the Bay of Bengal. This has resulted in a vast mangrove forrest.
  • Panchayat : Ramachandrapuram
  • Mandal: Vidavalur
  • Date of visit : 21.02.2011
  • Coordinates : 140 40107.1711–14045111.4311 N, 80005138.1711-80009108.2011E
What we find at Peddapalem- Ponnapudi in respect mangroves are actually mangroves of the Iskapalli lagoon. The Iskapalli lagoon is a narrow curvilinear brackish water body lying quasi-parallel to the shore line of Bay of Bengal .The lagoon is located at the northeastern part of the Pennar delta near Iskapalli village in Nellore district ,and is separated from the open sea by a 6 km- long and about 6 km-wide shore parallel sandy island, which is known as Kuratipalem island. .On the whole, with a water spread of about 10 miles2 (17.75 km2), including the tidal channel formed on the eastern side, the lagoon extends between latitudes 14O 40’ to 14O 45’N and longitudes 80O 05’ to 80O 10’ E. Another important aspect of the lagoon is that Pyderu. a 22 – km long rivulet that drains 50 km2 area in the northwestern Pennar delta directly empties into the lagoon.

True mangroves:
1. Avicennia marina 6-8 ft tall, no flowering
2. Rhizophora mucronata, 8-12 ft tall, one or two plants in flowering; no fruits.
3. Aegiceras corniculatum(L.) Blanco Myrsinaceae: 5-6 ft tall, flowering, no fruits.
4. Ceriops decandra (Griff) Ding Hou: Rhizophoraceae,5 – 6 ft tall, flowering; no fruits.
5. Excoecaria agallocha 6-8 ft tall, no flowers
6. Sonneratia apetala: No flowers; in fruiting condition. This species has been first identified by me in these swamps and has not been found in any other swamps of Nellore district I have so far visited.

Mangrove associates:
1. Acanthus ilicifolius L. – Acanthaceae, 4-5 ft tall, huge stands in flowering.
2. Aeluropus lagopoides (L.) Trin – Poaceae, flowering.
3. Fimbristylis ferruginea(L.) Vahl - Cyperaceae, flowering.
4. Ipomoea pes-caprae, flowering
5. Sesuvium portulacastrum, no flowers

Overall, the swamp is dominatd by A.marina . However.they are stunted, the tallest tree being not more than 8 ft. Next to A.marina, Acanthus ilicifolius is found in large numbers. A.ilicifolius communities are found at many points around the island. Such pure stands of A.ilicifolius is a rare feature in the mangrove swamps of Nellore district.

Wherever found, Aegiceras corniculatum is invariably associated with A.marina. Acanthus ilicifolius is found exclusiverly alone as pure communities, or associated with A.marina., Rhizophora mucronata is very sparsely distributed. The tallest tree is about 10-12 ft. True mangroves are found all along the fringe of the island and other creeks. In the interior of the island also which is waterlogged , both A.marina and Acanthus ilicifolius are noticed. On the whole, A.marina and other true mangroves are more robust and dense at the fringe of the island than at the boarding ferry point.

The mangrove swamps are reported to be revenue lands. At the periphery of the swamp, there is a mushrooming of salt pans, at East Gogulapalli of Allur mandal. There are also shrimp ponds around the swamp. The brackish water of Pyderu - sea are pumped in to the ponds. There is a lot of fishing activity in the brackish water. The fishermen are conscious of the significance of mangroves. Some of them reported that they venerated the mangroves. In spite of this, there is a lot of felling of A.marina for firewood and fencing. They reported that the fuel of A.marina is superior to mesquite. High tide is reported to prevail up to 11 am and low tide after that time.

Significantly, mesquite is absent anywhere around or in the interior of the Kuratipalem island or at the fringe of the Pyderu stream. It is found only landward along the ferry boarding points. This swamp is superior in terms of extent, diversity, density and robustness of mangroves compared to the three swamps visited so far.

Water and sediment samples are collected at 3 stations quite apart, in the swamp. At the first station where the samples are collected A.marina are dominant.

Water salinity : 21 ppt
Dissolved oxygen: 08.6
Water temperature : 26OC

At the second station R. mucronata are dominant
Water salinity : 20 ppt
Dissolved oxygen: 07.6
ater temperature: 27OC.

At the third station called ‘Cheruvu kalva’ both A.marina and R.mucronata are found.
Water salinity: 20 ppt
Dissolved oxygen : 08.5
Water temperature: 270C

Evidently, both salinity and dissolved oxygen are almost uniform throughout the three stations.

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