SALT MARSH FIELD TRIP GUIDE 2020 - Knysna Basin Project

2020

 SALT MARSH FIELD
 TRIP GUIDE
 NOS’PHAMANDLA NDAMANE

This guide was developed through funding received from Table Mountain Fund

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Table of Contents

1. About this guide .............................................................................................................................................. 3
 1.1 Using this guide ....................................................................................................................................... 3
 1.2 What is a salt marsh?............................................................................................................................. 3
 1.3 Salt marsh facts ........................................................................................................................................ 4
 1.4 Threats to salt mashes .......................................................................................................................... 4
2 Salt marshes in Knysna ................................................................................................................................ 4
 2.1 Site 1: Scouts hut ..................................................................................................................................... 5
 2.2 Site 2: Green Hole ................................................................................................................................... 6
3 Salt marsh vegetation:.................................................................................................................................. 8
 3.1 Cord grass (Spartina maritima): .................................................................................................... 8
 3.2 Soutbossie (Bassia diffusa): .............................................................................................................. 8
 3.3 Hairy plantago (Plantago crassifolia): ......................................................................................... 9
 3.4 Sea lavender (Limonium scabrum): .............................................................................................. 9
 3.5 Glasswort samphire (Sarcocornia perennis):............................................................................ 9
 3.6 Arrow grass (Triglochin buchenaui):.......................................................................................... 10
4 Salt marsh invertebrates: .......................................................................................................................... 10
 4.1 Marsh crab (Sesarma catenata): ................................................................................................... 10
 4.2 Common sand hermit crab (Diogenes brevirostris): ......................................................... 10
 4.3 Sandflat crab (Cleistostoma edwardsii): .................................................................................. 11
 4.4 Estuarine mud prawn (Upogebia africana):........................................................................... 11
 4.5 Tick shells (Nassarius kraussianus): ............................................................................................ 11
 4.6 Lesser heart clams (Dosinia hepatica): ..................................................................................... 12
5 Birds: ..................................................................................................................................................................... 12
 5.1 Egyptian geese (Alopochen aegyptiacus): .............................................................................. 12
 5.2 Grey heron (Ardea cinerea): ............................................................................................................ 13
 5.3 Blacksmith lapwing (Vanellus armatus): ................................................................................. 13
 5.4 Sacred ibis (Threskiornis aethiopicus): ..................................................................................... 13
6 Linking saltmarsh studies to the CAPS ............................................................................................. 14
7 Activities ............................................................................................................................................................. 16
 7.1 Using quadrats on the salt marsh ................................................................................................ 16
 7.2 Salt marsh crossword .......................................................................................................................... 18

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1. About this guide
This guide provides information on how to conduct a salt marsh field trip for teachers and
environmental education coordinators in the Knysna estuary. This document may be used in

conjunction with the Curriculum and Assessment Policy Statement (CAPS) document at
both primary and high school level. It is designed to support the learner’s understanding of

salt marshes with a specific reference to the Knysna estuary.
The importance and benefits of salt marshes are also highlighted in this guide.

1.1 Using this guide
This guide may be used to:
 • Understand what a salt marsh is,

 • The importance of salt marshes,
 • Threats to salt marshes,

 • Link the CAPS document to salt marshes,
 • Familiarise oneself with the salt marshes of Knysna,

 • Conduct activities on the salt marsh.

1.2 What is a salt marsh?
Salt marshes are often overlooked when counting the natural treasures of an area. Salt

marshes are coastal ecosystems between land and open saltwater or brackish water that is
often flooded by the tides. The tides and water flowing in from the surrounding catchment

carry in nutrients that stimulate plant growth in the marsh. Many of these plants are
halophytes (salt tolerant), however, each plant has a different tolerance level. Plants that are

at the low tide level are usually flooded at every tide and exposed during low tide meaning
they would have a high salt tolerance as opposed to plants at the high tide level that are

only flooded during extremely high tides and during storms. It is a combination of these
plants that form a salt marsh. Factors such as temperature, water level and oxygen also

determine how plants adapt.

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A saltmarsh acts as a buffer between land and sea that catches and filters sediment and

nutrients and provide protection against floods. Marshes also act as nurseries to juvenile
fish and invertebrate species.

1.3 Salt marsh facts
 • Salt marshes are among the most productive ecosystems on earth due to the tides
 which carry in nutrients for plant growth and carries out organic material to feed

 coastal organisms.
 • They provide flood and storm protection as a result of the ability to trap nutrients

 and sediments and build organic matter, keeping up with the rising ocean.
 • Salt marshes also provide a habitat for many animals.

 • A healthy salt marsh removes pollution from the water.
 • Serve as nature reserves.

 • Have a high biological productivity due to the nutrient and organic matter cycling.

1.4 Threats to salt mashes
 • Urban development

 • Pollution
 • Alien species

 • Sea level rise
 • Habitat loss and degradation

 • Industries
 • Erosion

2 Salt marshes in Knysna
There are several salt marshes around the Knysna estuary, however, there are only a few
sites that are accessible to conduct a salt marsh excursion. We have highlighted two sites

where one can conduct an excursion.

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2.1 Site 1: Scouts hut
GPS Coordinates: 340 04’ 42.8’’ S, 230 04’ 06.1’’ E

Street address: 1st Knysna Scout Hall, George Rex Drive, Fisher Haven, Knysna, 6571

 Figure 1: Street view of Scouts hut, (Photo: Nos’phamandla Ndamane,2020).

 Figure 2: Scouts hut salt marsh, (Photo: Nos’phamandla Ndamane, 2020).

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Figure 3: Scouts hut, (Source: Google maps, 2020).

2.2 Site 2: Green Hole
GPS Coordinates: 340 07’ 12.00’’ S, 230 06’ 56,46’’ E

Street address: 23 Woodbourne Drive, Leisure Island, Knysna, 6571

 Figure 4: Green hole, (Photo: Nos’phamandla Ndamane, 2020).

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Figure 5: Green hole salt marsh, (Photo: Nos’phamandla Ndamane, 2020).

 Figure 6: Green hole, (Source: Google maps, 2020).

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3 Salt marsh vegetation:
Vegetation on a salt marsh is important as it helps to reduce erosion, provide a habitat for

animals and provide organic matter to the surrounding system. Many plants found in salt
marshes are adapted to the ever-changing salinity, tide and nutrient levels. Listed below are

the common plants found in the salt marshes of Knysna.

3.1 Cord grass (Spartina maritima):
This type of grass belongs to the Spartina genus, it is

also commonly known as marsh or salt grass. They
form dense colonies just below the high tide mark

and are in some cases planted as sediment binders
to prevent erosion. This plant is important to the

health of the marsh due to the high volume of
organic material it contributes during decomposition.

This organic material acts as an important source of
food for various other animals.
 Figure 7: Cord grass,
 (Photo: Frances Smith, 2019).

3.2 Soutbossie (Bassia diffusa):
This plant has short underground stems with upright

branches that are surrounded by green succulent
leaves. Soutbossies grow high on estuarine shores, in

the sandy areas that lie close to or just above the high
tide level. The name Soutbossie is Afrikaans, meaning

“little salt bush” as the plant retains salt in its leaves
turning it a red colour. The redder – the more salt, Figure 8: Soutbossie,
 (Photo: Frances Smith, 2019).
thus, if it is very dry, with limited freshwater inflow etc.
– the leaves would be redder.

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3.3 Hairy plantago (Plantago crassifolia):
This plant has narrow, hairy, succulent leaves. It

usually grows in clumps and is found in the mid tide
zone as it grows well in moist soils. Flowering time is

usually from December to June.

 Figure 9: Hairy plantago,
 (Photo: Frances Smith, 2019).

3.4 Sea lavender (Limonium scabrum):
Sea lavender is a herbaceous perennial plant with
leaves growing in a dense basal rosette. Many species

of this plant flourish in saline waters, therefore
making them common in estuaries and marshes. The

flower color is a pink, violet to purple in colour.

 Figure 10: Sea lavender,
 (Photo: Frances Smith, 2019).

3.5 Glasswort samphire (Sarcocornia perennis):
Samphire is a sprawling perennial succulent with joint
stems and no obvious leaves. It forms mats on salt

marshes. It is also referred to as “sea asparagus” or
“sea beans”. Glasswort samphire is sold commercially

as it is edible. The name “glasswort” comes from the
fact that ashes of marsh samphire were once used to

make soap and glass.

 Figure 11: Glasswort samphire,
 (Photo: Frances Smith, 2019).

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3.6 Arrow grass (Triglochin buchenaui):
Arrow grass is a perennial with parallel lines on its

narrow linear leaves. Arrow grasses are used as food
plants by some juvenile fish. It is classified as aquatic

or semi-aquatic.

 Figure 12: Arrowgrass,
 (Photo: Frances Smith, 2019).

4 Salt marsh invertebrates:
The salt marsh is home to many animals. Below is a list of some of the animals that one can
find in the salt marshes around Knysna.

4.1 Marsh crab (Sesarma catenata):
Marsh crabs live in burrows in the mud. They are
identifiable by their square upper shell and brown-

yellow nippers with a furry lining around the hinge.
They feed on organic matter, microorganisms and

scavenge on dead animals.
 Figure 13: Marsh crab,
 (Photo: Frances Smith, 2019).

4.2 Common sand hermit crab (Diogenes brevirostris):
These animals have a left nipper that is thorny and
larger than the right. Their bodies are dirty-white with

darker speckles and spines and brown stripes on the
last segments of walking legs. They bury themselves

in sand when left exposed by tidal fluctuations.
Hermit crabs are known for colonizing and fighting

over empty gastropod shells to protect their soft-
skinned abdomens. Without these shells they would Figure 14: Common sand hermit crab in
 water, (Photo: Frances Smith, 2019).
hurt themselves.

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4.3 Sandflat crab (Cleistostoma edwardsii):
This crab is flat, sandy colored with a circular body. It

feeds on fine particles of detritus. This animal scuffles
under the sand in waterlogged areas.

 Figure 15: Sandflat crab,
 (Photo: Frances Smith, 2019).

4.4 Estuarine mud prawn (Upogebia africana):
These animals live in the intertidal zone, in the

muddy sand. Their first two walking legs have a spine
at the base pointing inwards, it’s robust and has a gut

that is laden with symbiotic bacteria which may
supplement its food. It is also a filter feeder usually

found on the lower edges of a saltmarsh. Fishermen
 Figure 16: Mud prawn,
commonly use them as bait. (Photo: Frances Smith, 2019).

4.5 Tick shells (Nassarius kraussianus):
These shells are globe shaped with a smooth spire.

They are usually 7- 10 mm in size. These animals are
found in estuarine mud banks and are usually

referred to as the hoovers of the ocean as they play a
big role in cleaning up dead and dying matter.

 Figure 17: Tick shell,
 (Photo: Frances Smith, 2019).

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4.6 Lesser heart clams (Dosinia hepatica):
Lesser heart clams are usually smaller than heart shaped clams, they have a smooth brown

exterior and have violet internal markings. These animals are usually less than 25 mm in size.
Clams are filter feeders. They draw in water and food particles through their gills which is

then filtered through their stomach. All bits in the water is then captured and eaten.

 Figure 19: Outside of lesser heart clam, Figure 18: Inside of lesser heart clam,
 (Photo: Frances Smith, 2019). (Photo: Frances Smith, 2019).

5 Birds:
Many birds frequent the salt marshes of Knysna. They use the salt marsh for different
reasons, some as a feeding spot and others as a place to make a nest and breed. Listed

below are birds that may be commonly found on the salt marsh in the Knysna estuary:

5.1 Egyptian geese (Alopochen aegyptiacus):
Egyptian geese are large water birds with dark

chocolate brown eye patches. The female looks
similar to the male apart from having darker markings

on her beak. They are often found around wetland
habitats such as estuaries and marshes. These birds

are usually found in flocks and are usually non-
 Figure 20: Egyptian geese,
migratory. They are aggressively territorial,
 (Photo: Frances Smith, 2019).
especially during breeding season. Egyptian geese are
mainly herbivorous.

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5.2 Grey heron (Ardea cinerea):
As implied in the name, this heron is mainly grey in

colour with a white head and a black streak extending
from the eyes to the neck. They are normally solitary

birds and are only found in groups during the
breeding season. They feed on fish, amphibians,

insects, crabs and small birds. The Grey heron has also
 Figure 21: Grey heron,
been known to feed on the Knysna seahorse. (Photo: Frances Smith,2019).

5.3 Blacksmith lapwing (Vanellus armatus):
These birds get their name from the sound they make
which is similar to a blacksmith’s hammer striking

metal. This bird is marked in shades of black, white
and grey. They have grey and black wings, while the

rest of the body and the head are boldly patterned in
white and black. Males are usually smaller than the
 Figure 22: Blacksmith lapwing,
females. They live in areas with short open grass, (Photo: Frances Smith, 2019).

where there is plenty of water such as marshes and

estuaries. Searching for food is done on foot where they feed on small aquatic and
terrestrial invertebrates and some plant material.

5.4 Sacred ibis (Threskiornis aethiopicus):
The Sacred ibis is mostly white with a black head, neck
and plumes at the tail. It also has a long, slender,

down-curved black beak which they use to dig for
food in shallow waters. They are mostly found in large

colonies near waterbodies such as marshes, estuaries,
lakes and wetlands. They feed mainly on insects such
 Figure 23: Sacred ibis,
as grasshoppers, crickets and locusts and on garbage. (Photo: Frances Smith, 2019).

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6 Linking saltmarsh studies to the Curriculum Assessment Policy

 Statement (CAPS)
The aim of linking local resources such as the salt marsh to the CAPS document is to show

learners the value of local resources and the educational benefits they offer. It is also a way
of raising awareness around conserving these resources that may otherwise be overlooked.
 Grade/Subject Topic Link Relevance to Rocky shores

 10 T3: Gr.11 T1: A salt marsh may be used to show
 Biosphere Biodiversity of biotic and abiotic factors and how
 to Ecosystems Animals these influence the diversity of
 animals found there.

 Gr.11 T2: Energies (light, carbon dioxide,
 Energy temperature) determines how an
 Transformations ecosystem function. Use the salt
 marsh as an example of how an
 ecosystem functions and how the
 various functions are beneficial to the
 animals and plants found there.

 Gr.11 T3: Tidal influence and other
 Interactions in the environmental factors have an impact
 environment on how animals and plants interact,
 behave and adapt on the salt marsh.

 Gr.11 T4: Human actions affect the state of an
 Human impact on ecosystem as well as the biodiversity
 the environment of an ecosystem. Explore the effect
 that humans have on salt marshes.
 Also, look at past examples where salt
 marshes have been destroyed for
 urban development.

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T4: Gr.11 T1: Explore the biodiversity (plant and
 Classification Biodiversity of animals) on a salt marsh and what
 Schemes Animals affects it. Identification and
 classification of animal and plant
 species.

 Gr.11 T3: Explore how the different
 Life processes in requirements for gaseous exchange in
 Plants and plants and animals are met with a
 animals specific reference to salt marsh plants
 and animals.

Geography Gr.10 T1: Life Sciences: Tides affect ecosystem functionality.
 The Biosphere to During the excursion it can be shown
 atmosphere ecosystem how tidal changes influence a salt
 marsh and the distribution of different
 plant and animal species.

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7 Activities

7.1 Using quadrats on the salt marsh
Aim: To identify animals and plants on the salt marsh

To work in groups: The learners should be arranged
in small groups. Each group will be assigned a

transect (a straight line through a natural feature
where measurements are taken) which they will use to

place their quadrats - a square frame that is used to
demarcate a small area to study the density or
 Figure 24: Example of a quadrat,
abundance of an item. (Photo: Frances Smith, 2019).

They will then have to identify what type of animal or plant they found in the quadrat (to
phylum level, if they can) or provide a description if they don’t know what it is. To do this

they may use any resource (book, internet, teachers). They are required to put the data in
this table.

Results:
 Quadrat Plants % Cover Animals Number

 1.

 2.

 3.

 4.

 5.

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For plants, we use percentage cover, this refers to an estimate of what percentage of an

area enclosed by the quadrat is occupied by each species. This is calculated by using the
following formula:

 = x 100
 
The other option would be to use the picture below as a guide. This is whoever, subjective.

This link has additional information:
(http://www.seagrasswatch.org/Methods/Field_handouts/SeagrassWatch_Fiji_fieldbooklet.pdf)

After, the learners will note which animals
they saw the most in each quadrat and

any interesting things they noticed and
perhaps relate their findings to factors

such temperature, tide level and salinity.
They may also explain how they think the

animal is adapted to that area.
If there is scope, the teacher may print a

list with the common species found on the
salt marsh.

 Figure 25: Example of how to determine %cover. (Photo:
 Marine planet ecology group,2003).

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7.2 Salt marsh crossword
Aim: Expose the learners to new words to familiarise themselves with words commonly used

when talking about the estuarine environment.

 T M F C T G L G A H C Y P L A P F H W D
 C R N Y Z Q H G K K Q N Z F G N X D Q F
 L L X W U J P Y C R N Q M Z W J Y J D W
 Y N B E U A F Z U C H T H N X Z S Z H N
 D X Z V T X Z M T V W N Q H R U F W U Y
 J N M S D G R N M C Q H F S W I W Z B A
 K I B O Y G G N D F E D C P I D K N S Q
 X K Z U U A F B P H G I H E W W U E P R
 L W X L Y Q C F X J D O G A I J X G I R
 A N U P Z Z S Z U N C Y Q J H E R T S Z
 N Y C N G G O L D S T I V Y N I Y Y B Y
 L Z D C R Z W E K K G W W A Y G N G Z M
 B E O B A O I Z W J O Q X O P Q P Q X K
 C E J J X A Z E E W J Q J C J F R N X B
 G M S W E B H C L F I D L D C P O G W U
 X A U J N L Q M J K O K W B J V C B A C
 U I K K I A T J T S D E B F H S L Z Y H
 C D K A O O A I E K C P K E X V D Z M P
 N F V P N C Z J V N P F S Y P N J V S C
 O U Y B Y H F W A Y K D U W Z B Q I K H
 E J V X N R E K H L D U O B N O I G U G
 V Y E K I H K R T V G W P B D W W A E E
 U Z N R A G U X W E R O T U I Y R X V T
 W B G B Z V Q R U I F Q V T A B C Z D E
 H V G S M O U Y B P O X V E A L Z R L Q
 H W X G W R Y S E W N P C Z M E Q J C O

 List of words
 Mud crab Tides Eelgrass Cordgrass Filter
 Nutrients Erosion Soutbossie Land Marsh
 Biodiversity Pollution Mud prawn Nurseries Saltwater

As an additional exercise for the older learners, they could be asked to find out why these
words are associated with estuarine environments, specifically the salt marsh environment.

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