RiverWise
Issue 21 ~ January 2020
The monthly newsletter of the Lower Breede River Conservancy Trust
How your membership
can help the Breede
All estuaries in South Africa are under severe pressure resulting from over-exploitation of natural resources, habitat destruction and deterioration of water quality.
If you take an active interest in, or use, the Breede River Estuary we hope that we can persuade you to become a member of the LBRCT and to support our endeavours on your behalf by way of your contribution to these efforts.
The authorities who are ultimately responsible for ensuring protection of our valuable natural resources are contributing, however, they simply cannot afford to allocate sufficient of their available funds to meet the estuary’s conservation needs.
Your membership contribution supplements the funds obtained from the licence fees paid by users of boats; the municipalities by way of supplementary grants constrained by their many other social upliftment and development imperatives, and grants from those government agencies to whom we are contracted.
There are 62 estuaries in the Western Cape and all need support. The Breede is one of the two largest and most important and we all need to play a role in preserving it. 100% of your membership subscriptions are put to the best possible use to help maintain the conservation infrastructure that has taken many years to put in place and initiate new projects such as:
• Turtle and penguin rescue transport
• Environmental education programmes
• Holiday activity programmes
• Funding conservation interns
• Printing brochures, pamphlets, posters and information packs
• Producing and erecting signage
• Materials and equipment for monitoring projects
For R 100 a year, you can assist us with all of the above and add your voice that is so important to ensure that your opinions and concerns are heard. The LBRCT can speak more authoritatively when dealing with the vast number of threats, regulations and legislation that already affect the estuary with the backing of a sizeable member base.
Please think about the future of the estuary and the importance of maintaining its good health for you and your children’s benefit through supporting our effort.
In this issue
This issue covers our activities for both December 2019 and January 2020. First up is a season report on our holiday programme over the unusually windy festive holidays. We also observed dieback in the eel grass in Skuitbaai, as well as hundreds of pufferfish washing up in January. Our species of the month is the Common-ringer plover, and we close off with summaries and data from our routine monitoring projects covering water quality, birds counts and marine deris.
Season report
This season we saw some highly variable conditions affecting how and when visitors could ustilise the estuary and sea. While we had a little rain mid December, it did not deter resolute fisherman from going out on the water, and neither did we notice much change in the flow from up river. However, the rains in January did deliver significantly more water in the catchment area. We observed flow increases from 19 January at 21:48, with flow (volumetric discharge) peaking at 144.16 m³/s and stage (water level surface elevation) at 1.627 m on 21 January at 05:48 at the Swellendam gauge.
On the wind side, the table below shows the averaged comparitive wind data for the same periods of 4 November to 26 January for 2018-2019 and 2019-2020. The red indicates much windier conditions this period, and green quieter wind compared to the previous period. Winds were also more predominantly westerly this period, compared the a more northern direction in the previous period.
Holiday Programme
The LBRCT hosted several events during the holiday season with some great turnout at our sandcastle competitions in Infanta and Witsand. We also hosted beach clean-ups on both sides of the river mouth with lots of litter being picked up on both occasions. A shout out must also go to our prize sponsors at Pili Pili Witsand, Anchorage Restaurant and Grunter Malgas.
Sand castle competition
December beach cleanups
Kids colouring competition winners
During December we also ran a colouring in competition at Pili Pili Witsand, Anchorage Restaurant, Grunters Malgas and River Breeze Resturant. We had over 50 entries with the youngest coming in at 1.5 years old and the oldest at 13 years old. Thank you to all who entered. Congradulations to Hanri (10) and Karla (5) who were selected as our winners!
Unusual and interesting observations
Cape dwarf-eelgrass (Zostera Capensis)
This species of eelgrass is the dominant seagrass in South Africa and is found from the Olifants Estuary on the West Coast to Kosi Bay on the East. It is common in permanently open estuaries with marine conditions (35 Practical Salinity Unit) in the lower reaches. The cape dwarf-eelgrass can occur in salinities from 12 – 44 PSU but prefers salinities of 30-40 PSU.
The eelgrass beds in Skuitbaai show signs of a potential dieback or discoloration (large brown patches) while the LBCRT staff were on a foot patrol in the area. This needs to be investigated further before any conclusive explanation can be determined.
Researchers from Nelson Mandela University suggest that sudden changes to the surface salinity during the flood killed some sections of the eelgrass bed.
The cape dwarf-eelgrass can survive freshwater conditions, but biomass and bed density are reduced. Sudden reductions in salinity can cause damage to the plant and lead to mortality when the salinities increase again. Long-term exposure to freshwater conditions kill this submerged macrophyte.
Pufferfish and blue bottle strandings
During January, hundreds of pufferfish, mainly Evil-eye Puffers (Amblyrhychotes honckenii) washed up dead on the beaches in Witsand. This phenomenon was recorded on beaches between Cape Town and Port Elizabeth. The LBRCT removed over 440 of these fish from our beaches. Most of the blaasops were picked up between Blokke and @Anchorage Restaurant and Bar. These tropical fish are highly poisonous.
A possible reason for these fish washing up onto our shores is due to the big seas and strong winds experienced at the time. These weather conditions can frighten or disturb these fish which causes them to inflate their abdomens and they then wash up on the beach. Another potential reason are the spawning aggregations that take place in shallow water. During these rough seas, the puffers can get blown ashore which results in mass mortalities for this species.
Along with these fish, many blue bottles (Portuguese man o’ wars) also washed up. These siphonophores are not true jellyfish and live on the ocean’s surface being propelled by winds, currents and tides. The rough sea conditions and onshore winds would have pushed these animals onto the beach.
New projects
Vegetation and habitat maps
During January we had the pleasure of hosting staff from Nelson Mandela University to assist us in updating our vegetation and habitat maps and species identification along the estuary. Mapping occured on land and by boat, looking mainly at salt marshes, eel grass and reed beds. We also received advice on possible rehabilitation projects to reduce the erosion we observed in the salt marsh banks. All of the information collected will go into our GIS system, and provide information at much finer resolution than the existing maps.
Alien removal
Once the bussle of season was over, we could allocate more manpower to the manual removal of water hyacinth and parots feather above the pont. Water hyacinth is a highly invasive plant that is South Africa’s most damaging aquatic weed. This plant species is originally from the Amazon basin in South America. It is is now found throughout the world, clogging up water ways and degrading aquatic ecosystems. This plant forms dense mats on the waters surface and negatively affects river flow and reduces biodiversity in a system.
Species of the month:
Common-ringed Plover
Photos by Craig Midgley.
The Common-ringed plover or Ringnekstrandkiewiet is easily identifiable from other plovers by the yellow-orange bill with a black tip, orange legs and a white collar above a blackish breast. Breeding adults also have an orange eye ring.
Common-ringed plovers have a circumpolar breeding distribution and are mainly found above 60° North (latitude). It is believed that the birds that migrate to southern Africa are from the far north of their breeding range and travel 18000 km to reach our shores.
In southern Africa these birds are a common non-breeding visitors that arrive in September and leave by April. It is estimated that there are 11 000 of these plovers along the coast in southern Africa, excluding Mozambique. The oldest known bird was 19 years and 11 months old. The current worldwide population trend for this species is decreasing.
These birds are found in coastal habitats with a preference for muddy estuaries. Hundreds of these plovers can be found on the exposed mudbanks during low tide on the Breede River Estuary during spring and summer.
They feed on small crustaceans (e.g. crabs, shrimps, prawns etc), marine polychaetes (segmented worms), amphipods, isopods and insects. They feed during the day and at night.
-- Chittenden H, Davies G, Weiersbye I. 2016. Roberts Bird Guide: Second Edition
In the data
Monthly routine monitoring
January water quality
Two water quality runs were conducted during January; one before the rain and one afterwards. The salinity values before and after the rain showed a marked difference with much lower salinities recorded after the rainfall. These lower salinities are a result of increased freshwater in the estuary. The salinities near the mouth were typical for summer (34.65 PSU) before the rainfall, while the second survey recorded at maximum value of 10.12 PSU. During the first survey, freshwater conditions (less than 0.5 PSU) were not recorded, but were however observed from Powerlines during the post rain survey.
Water temperature and secchi depth were also impacted by the freshwater in the estuary. The water temperature during the first run ranged from 23.16 °C to 27.2 °C , while after the rainfall ranged between 20.06 °C to 23.21 °C. Secchi depth (water transparency) was reduced from an average of 1.7 meters to 0.3 meters. River runoff into the estuary increases the suspended solids in the water column and it becomes more turbid which decreases the water transparency.
Salinity
Temperature
Secchi depth
December / January bird counts
The number of species for December 2019 (33) was higher than those recorded in January 2020 (26), but the total number of birds was higher this month (1161 birds) compared to the previous month. The five most abundant species recorded during December were South African Shelducks, Egyptian Geese, African Sacred Ibis, Grey Plovers and Common-ringed Plovers. Two of these species recorded an increase in relative abundance in January: South African Shelduck and Grey Plover.
The shelducks accounted for 18.5% of all birds in December, but increased to 25.4% in January. Grey Plovers increased from 5.0% to 6.3%. Common-ringed plover remained relatively stable at 21% between the two surveys, while Egyptian Goose decreased from 14.2% to 10.8% of all birds recorded. African Sacred Ibis recorded the largest decrease from 8.2% to 2.7% in January.
Whimbrel (6.5%), Blacksmith Lapwing (6.03%), Common Greenshank (5.2%) and Kelp Gull (5.8%) all saw increases of at least 2% in relative abundance in January.
Some of the species missing in January are uncommon birds (Terek Sandpiper) or difficult to spot (Lesser Swamp Warbler and Malachite Kingfisher) so don’t always get seen on surveys. Southern Red bishops were not seen in January and one reason for this is could be that the main breeding season is finished, and most birds have moved to form large flocks away from the reeds. These birds still use reedbeeds to roost.
Both the December and January bird counts were recorded outside of the main holiday season.
December 2019
January 2020
December / January marine debris
Main Beach
The litter picked up at this site was dominated by plastic in December (86.9%) and January (82.5%). For both surveys, more than half of the plastic picked up was considered microplastics and large plastic pieces. When plastic has been broken down to such small pieces it is often impossible to tell where the it originated from. However, in December over 30% of the plastic recorded were tiny plastic pellets called nurdles. Nurdles are deposited on our beaches from the ocean as they originally come from Durban.
Gov. Slip
Smoking-related litter comprised approximately 20.0% of all litter from Gov. Slip to Skuitbaai in both months. The biggest culprit were cigarette butts. Most of these were not degraded and suggests this litter is from beach users and is not imported into the system. Polystyrene pieces are an important litter type in this survey area as it accounted for 25.2% and 23.6% in December and January respectively. This litter type is most common at this site which suggests the original source of the polystyrene is upriver. Plastic litter was also recorded at this site and increased over the two months: December (19.7%) and January (41.2%). Rope pieces from commercial trawlers increased from 1.8% to 9.7%.
Blokke
There was a difference between the type of plastics most commonly recorded between the two survey months. In December, plastic litter (51.2%) was dominated by pieces of plastic (large and microplastics). In January there was a significant increase in plastic bags to the overall litter recorded. A two-fold increase in plastic bags was noted: 9.1% to 20.8%. Many of these bags were found at the low tide line. This in combination with an increase in plastic bottles 1.2 – 3.9%, with foreign logos and writing, suggests this litter is from vessels that are far offshore. Litter associated with beach users also increased marginally: fishing-related litter increased to 3.2% compared to the pre-holiday season survey in December (2.3%). Food wrappers, a beach user source of litter, increased from 3.7- 5.6%.
Oysterbeds
In each of the two months, the type of litter recorded differed. In December, glass (41.6%) and plastic (32.3%) were important while in January glass-based litter was down to 2.8%. Plastic litter increased to 62.4%. Plastic-bottle caps, particularly those from beverage bottles, increased from 3.0% to 12.7%. Similarly, plastic bottles recorded an increase from 2.4-4.3%. The largest increase occurred with plastic non-grocery bags (6.3% to 18.4%). Many of which were fishing related packets (glowstick, bait, hook and swivel packets) which suggests local beach users. Food wrappers also increased almost three-fold from 4.8% to 14.2% in January.
Oysterbeds appears to get most of its litter from beach users while Main Beach and Blokke were dominated by litter that likely had a marine origin and washed up onto our beaches. This was evident even more so in January. The strong onshore winds during December could have be the reason for more marine litter being recorded on the Main Beach and Blokke survey sites.
Cumulative marine debris collected for all areas:
December 2019
January 2020
Thank you for reading
We hope you enjoyed this months' issue. Should you have any feedback, questions, or matters you would like us to cover in a future issue, please do not hesitate to write to us at news@breede-river.org.