A Thesis Submitted to the Department of Biology In

ARBA MINCH UNIVERSITY SCHOOL OF GRADUATE STUDIES DEPARTMENT OF BIOLOGY

The Impact of Water Hyacinth (Eichhornia crassipes) on Composition and Abundance of Macrophytes and Phytoplanktons, and on Water Quality in Lake Abaya, Southern Ethiopia

BEDILU BEKELE MENGISTU

Advisor

DIKASO UNBUSHE (Ph.D.) A THESIS SUBMITTED TO THE DEPARTMENT OF BIOLOGY IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE MASTERS OF SCIENCE DEGREE IN BIOLOGY (BOTANICAL SCIENCE) FEBRUARY 2014 ARBA MINCH

ARBA MINCH UNIVERSITY SCHOOL OF GRADUATE STUDIES DEPARTMENT OF BIOLOGY

The Impact of Water Hyacinth (Eichhornia crassipes) on Composition and Abundance of Macrophytes and Phytoplanktons, and on Water Quality in Lake Abaya, Southern Ethiopia

A THESIS SUBMITTED TO THE DEPARTMENT OF BIOLOGY IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE MASTERS OF SCIENCE DEGREE IN BIOLOGY (BOTANICAL SCIENCE)

APPPROVED BY:

ADVISORS:

1. DIKASO UNBUSHE (Ph.D.) Sign date

EXAMINORS

INTERNAL

NAME

EXTERNAL

NAME

CHAIR PERSON

NAME

Declaration

I, undersigned, declare that the information provided in this thesis is an original work and that it has not been presented in other universities or collage, seeking for similar degree or other purposes. All sources of materials used in this thesis have been dully acknowledged

Bedilu Bekele

Sign date

Advisor:

1. Dikaso Unbushe (Ph.D.) Sign date

Dedication This work is dedicated to our planet which is found at most vulnerable condition facing towards pollution the physical environment leading to extinction of the biotic treasures.

III

TABLE OF CONTENTS

Contents pages Declaration ...... II Dedication ...... III TABLE OF CONTENTS ...... IV LIST OF FIGURES ...... VI LIST OF TABLES ...... VII LIST OF APPENDICES ...... VIII ACRONYMS ...... IX ACKNOWLEDGEMENT ...... X ABSTRACT ...... XI 1. INTRODUCTION ...... 1 1.1 Background ...... 1 1.2 Statement of the problem ...... 4 1.3 Objective of the study ...... 5 1.3.1 General Objective ...... 5 1.3.2 Specific objectives ...... 5 2. LITERATURE REVIEW ...... 6 2.1 Wetland definition and classification system ...... 6 2.2 Role of wetlands ...... 7 2.3 Threats to wetlands ...... 8 2.4 The consequence of wetlands loss ...... 9 2.5 Ethiopian wetland classification system ...... 11 2.6 Wetlands and water ...... 12 2.7 Vulnerability of wetlands to invasive species ...... 13 2.8 Taxonomy, behaviors, distribution of water hyacinth (Eichhornia crassipes) ...... 13 2.8.1 Distribution of water hyacinth ...... 15 2.8.2 Adverse Impact of water hyacinth on wetland ecosystem ...... 15 2.8.3 Beneficial impact of water hyacinth ...... 21 3. MATERIALS AND METHODS ...... 23 3.1 Description of study area ...... 23

3.1.1 Location of the study area ...... 23 3.1.2 Climate ...... 26 3.1.3 Plant and animals life of the study area ...... 27 3.1.4 Population and socioeconomic condition ...... 27 3.2 Design of the study area ...... 27 3.3 Data collection ...... 27 3.3.1 Macrophyte data collection ...... 27 3.3.2 Phytoplankton data collection ...... 28 3.3.3 Water quality data collection ...... 28 3.4 Data analyses ...... 28 3.4.1 Macrophyte distribution and abundance data analyses ...... 28 3.4.2 Phytoplankton distribution and abundance data analyses ...... 29 3.4.2.1 Waterbio physicochemical property analyses ...... 29 4. RESULTS AND DISCUSSION ...... 31 4.1 Abundance, composition and distribution of macrophytes ...... 31 4.2 Distribution and abundance phytoplankton ...... 39 4.2 Water bio physicochemical parameter measurements ...... 43 5. CONCLUSIONS AND RECOMMENDATIONS ...... 50 5.1 Conclusions ...... 50 5.2 Recommendations...... 51 6. REFERNCES ...... 52 7. APPENDICES ...... 58

LIST OF FIGURES Figure 1Macrophytes and their location ...... 3 Figure 2 Stepwise invasion process ...... 4 Figure 3 Production of fish and other crustaceans decline due to shrinkage of wetlands ...... 10 Figure 4 Map of Ethiopian wetlands, rivers and lakes...... 12 Figure 5 Morphology of the flower of water hyacinth ...... 14 Figure 6 Cascading effect of water hyacinth ...... 20 Figure 7 Map of Ethiopia showing location of the study area ...... 24 Figure 8 Landsat satellite image showing location of sampling sites of the study area ...... 25 Figure 9 Climadiagram of the study area ...... 26 Figure 11 Plant distribution based on different category types in study area ...... 32 Figure 12 Partial view of water hyacinth infested site in the study area ...... 34 Figure 13 Number of species versus water hyacinth spatial distribution ...... 37 Figure 14 Phytoplankton abundance distribution at family level between infested and non- infested site ...... 41 Figure 15 Phytoplanktondistribution(at family level)between infested and non-infested sites .... 42 Figure 16 Multiple correspondence analyses with two dimensions ...... 48

LIST OF TABLES Table 1 Major wetland ecosystem services to human benefit ...... 8 Table 2 Total suspended concentration estimated from turbidity measurement ...... 18 Table 3 Total macrophytes records in four sites ...... 31 Table 4 Macrophyte distribution status in site-1...... 33 Table 5 Macrophyte distribution status in site-3...... 33 Table 6 Macrophyte records from site-2 (non-infested sites) ...... 35 Table 7 Macrophyte records from distribution site-4 ...... 35 Table 8 Sorensen similarity index of the four study sites (beta diversity)...... 37 Table 9 Macrophyte diversity, evenness and richness in four study sites ...... 38 Table 10 Diversity, evenness and richness variation among study sites ...... 39 Table 11 Phytoplankton in water hyacinth infested sites and non-infested sites ...... 40 Table 12 Water bio physicochemical property distribution ...... 43 Table 13 ANOVA result of water physicochemical parameters...... 47

VII

LIST OF APPENDICES Appendix 1 Water Biophysicochemical correlation with water hyacinth ...... 58 Appendix 2 Descriptive statistics some water quality parameters infestation in site-1 ...... 59 Appendix 3 Descriptive statistic of some water quality parameters infestation in site- ...... 59 Appendix 4 Descriptive statistic of some water quality parameters infestation in site-2 ...... 60 Appendix 5 Descriptive statistic of some water quality parameters infestation in site-4 ...... 60 Appendix 6 Descriptive statistics of the total 60 plots ...... 61 Appendix 7 Discrimination measurement index ...... 62 Appendix 8 Some Water Biophysicchemicalmean values data from 60 plots ...... 63 Appendix 9 Some spectrophotometric reading for chlorophyll-a analyses ...... 65 Appendix 10 Somephytoplanktons found in study sites ...... 66 Appendix 11 Somemacrophytes from the study area ...... 68

VIII

ACRONYMS ANOVA Analysis of Variance

AMU Arba Minch University

[chl-a] Chlorophyll-a Concentration

DO Dissolved Oxygen

GF Glass Fiber

IBC Institute of Biodiversity and Conservation

NWHSP National Water Hyacinth Strategic Plan

NHWRP New Hampshire Water Resources Primer

TDS Total Dissolved Solutes

TFSS Total Fixed Suspended Solids

TSS Total Suspended solids

TVSS Total Volatile suspended solids

PCA Principal Component Analysis

pH Power of Hydrogen

SNNPRS Southern Nations and Nationality People‟s Regional State

SPSS Statistical Packages for Social Science

UV/VIS Ultra Violet/Visible

UNEP United Nations Environmental Protection

USEPA United States Environmental Protection Agency

WHO World Health Organization

ACKNOWLEDGEMENT

This is a miracle, Praise to God. In special way I would like to say thank you my advisor and teacher Dr. Dikaso Unbushe for his immeasurable help, guidance, comment and encouragement throughout my study period.

I would like to say thank you Ato Eyasu Shumbulo and other postgraduate instructors. I also thank AMU, Collage of Natural science and Department of Biology administrative staff for their support to get this program admission. I would like to say thank you in special way for the following persons: Ato Yared Godine, who helped me to get Meteorological data; Ato Aselle Ebella who helped me in data collection in the study area.

Finally I extend my gratitude to honest friends who helped me on their prayer at home town.

ABSTRACT The impact of water hyacinth (Eichhornia crassipes) on macrophytes, phytoplankton and some physicochemical parameters of water was studied in south western part of Lake Abaya in Gamo Gofa Zone, SNNPRS of Ethiopia. The study was made in two cases in which one with water hyacinth (Eichhornia crassipes) infested and the other with non-infested sites each one consisting of 30 plots. Macrophyte plant samples were collected, dried (using herbarium techniques) and identified (using Ethiopian flora). For phytoplankton studies, two liters of water sample were collected under sterile condition, filtered with 10µm pore size membrane filter, preserved with luglose solution and plankton identification was carried out using inverted microscope. The results showed that water hyacinth negatively affect the abundance of macrophytes by reducing 20% and changing the community into nearly monotypic. However, some macrophytes species from Poaceae and Cyperaceae family were observed to share the same niche with the alien plant. The results also indicated that water hyacinth affect phytoplankton abundance and distribution. Cyanophyceae, Bacillariophyceae and some Chlorophyceae were observed co-existing with the alien species whereas most Chlorophycaea and Dinophyceae were excluded from the niche. The less frequently occurrence of the nuisance Microcyst in infested sites might be contributed to some beneficial impact of the plant. The ANOVA result showed that except salinity there is significant variation of water quality measurements among groups (sites). The Pearson’s correlation analyses also showed that water hyacinth negatively correlated with turbidity, chl-a, DO, Salinity, conductivity and TSS, and positively correlated with TDS and pH of the water. In addition, multivariate correspondence analyses of discrimination measures showed that the alien plant discriminate some of water quality parameters like TDS, DO, TSS and Turbidity more than other macrophytes do. Water hyacinth has the potential to alter the floristic composition, abundance and diversity of plants of the wetland ecosystem. The spreading of the water hyacinth has to be checked and halted before it cause irreversible distraction on the ecosystem

Key words: Invasive plants, Macrophytes, Phytoplankton Water hyacinth, Wetland

1. INTRODUCTION

1.1 Background

Wetland ecosystems are ecosystems found in the transition area between terrestrial and aquatic ecosystems. They are the most productive ecosystems (Tharme et al., 2006). They constitute only 6% of the earth‟s surface (AbebeYilma, 2003). Wetlands possess unique types of flora and fauna which range from unicellular organisms to the giant multicellular reptiles, mammals and angiosperms. But these flora and fauna are not studied very well. There are several reasons for this. One reason could be they are under estimate in terms of their ecological advantage (Walter, 2002). The other reason could be their location which is not easy to handle and it is full of risk. Furthermore they do not have one and direct definition and as a result difficult to decide which wetland is truly a wetland and require protection or not (Walter, 2002).

Wetlands may be defined as areas that are inundated or saturated by surface or ground water at frequency and duration sufficient to support a prevalence of vegetation and organisms typically adapted to water saturated soil condition (Weiner 2013). Wetlands in Ethiopia are defined as land covered by shallow water encompassing lakes, rivers, swamps, floodplains, ponds, aquifers and dams (Leykun Abunie, 2003). Ethiopia‟s ecological and climatic variation is to a large extent linked to its highly variable geographical topography (Tsehaye Asmelash, 2009). The altitudes of the country range from 125 m below sea level in the Dallol depression, to 4,620 m above sea level at the top of Ras Dashen which encompasses different kinds of wetland ecosystems (AbebeYilma, 2003). Just to mention some of wetlands of the country, Asale and Afrera in Afar region; Lake Tana and Hayk in Amhara region; Ashengie in Tigray region; Gojeb, Bishoftu and Hora in Oromiya region; Abaya, Chamo and Hawasa lakes in SNNPRS and Baro River flood plains in Gambella regions (Leykun Abunie, 2003). These wetlands have several uses including Lake Tana for tourism is a source Blue Nile; Lake Hayk for fish production; most lakes of rift valley for fishery and tourism and Baro River basin for transportation.

The plant community types in wetland ecosystem differ from that of dry land ecosystem. The plant types must have the characteristic features that enable them to live relatively unstable habitat. The wetland ecosystem is unstable in physical and chemical conditions (Florida, 2007).

Frequent water wave disturbance, siltation and effluents of chemicals from terrestrial land into water body are attributes of the ecosystem. Competition within the community is also a common feature. The plant that fit the ecosystem more influences the others. Those outstanding plants have better morphological and physiological adaptations for nutrient utilization; allelopathic resistance and resistance to anoxic condition than the rest. In general the plants that grow in wetland ecosystem clumped together as weeds (Schmidt and Kannenberg, 1998).

These weeds can be classified traditionally as emergent; floating leaved and submersed types (Roberta and Williams, 2007). But other scholars classified them into four (figure-1) by adding free floating plants (Florida, 2007; Richard and Lamberti, 2007). Emergent macrophytes are plants that emerge at the littoral and semi dry area of the wetland. Plants like Typhaceae, most Cyperaceae and Poaceae are included in this group. Emergent plants grow at the edge of water ponds, lakes and rivers. They relatively stable community regardless of the availability and quantity of water. Floating leaved macrophytes are plants rooted to the bottom but their leaves float on the surface. They are obligate water dependent plant because they require water as mechanical supporter for lifting up their leaver over surface. They are less affected by the quantity of water. A typical example these plants include Nympheae. Submerged macrophytes are plants that grow completely under water. Plants like Isoetes can be mentioned under this group. These groups of plants are highly affected by the availability of water. Not only the quantity of water but also quality of water can also affect the normal growth of these plants. Free floating plants are plants that float on or just under the surface of water. Lemna, water hyacinth and water lettuce are some common plants under this group (Steven et al., 2007).The floating leaved macrophytes and submerged macrophytes collectively called euhydrophytes (true water dwelling plants).

Figure 1Macrophytes and their location (Steven 2007) As already mentioned, wetlands constitute only 6% of the world ecosystem but they possess 33% of invasive plants species of the planet (Kohl, 2011). This shows that how wetlands are vulnerable to invasion. Of course, these ecosystems are much enough to support a great number of organisms and with high diversity since they are found on alluvial soil which is rich in nutrients. This might be the reason why they are susceptible for invasion (Zedler, 2004). Even though there were speculations that more diverse community is less susceptible to invasion, the ideas now are being disproved with recent studies. An invasive species is defined legally in the USA as “An alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health. Alien species means, with respect to a particular ecosystem, any species that is not native to that ecosystem (Mark, 2012). However, a plant which is invasive to region may or may not be invasive to the other region (ISAC 2006). Most of these introduced plant species cause serious impact on ecosystem. They out compete with native plants and establish a monotype community. This change of the community type leads to change of normal functioning process of the ecosystem resulting in limited ecosystem services. It is clear that the befit gained from more diverse community is much greater than from a monotypic one. Invasive plants alter the ecosystem functioning by altering soil and water chemistry, nutrient cycling, hydrology and disturbance regime of the infested ecosystem. Beside this they affect seedling recruitment blocking seed dispersal through their thick mat growth of stem, root and rhizome (Shibu et al., 2013)

The spread and impact of invasive species is a stepwise process that happens over time. Non- native species must pass through at least three steps before they cause economic and ecological impact (Julie et al., 2007). Figure 2 below illustrates the three stages of invasion. Transportation stage of seeds, spores, or fruits of the plant is carried by human, animals, winds or other transporting vectors. When the transported plant arrives to a new area, it stars to establish and familiarize itself with the new environmental condition. During this stage, the alien plant highly utilizes the resources and grows fast. This stage is relatively takes longer period of time. At the end of establishment stage the alien plant produce large number of propagules which are ready to occupy a new area. Introduction and establishment stage are hidden stages. Finally, the propagules with the aid of dispersing agents colonize another area and the cycle continues.

Transportation and Spreading and cause introduction to new Establishment impact area

Figure 2 Stepwise invasion process (modified from Julie et al., 2007). Recent reports showed that the spread of invasive species is neither easy to manage nor simple to reverse the destruction it brought (UNEP, 2013). Howard (2002) also affirmed this and mentioned that it is difficult to control, eradicate and even to detect invasive species especially in an aquatic ecosystem. However Charles and Ducks (2006) suggested that it is important to predict which species cause serious impact on ecosystem and how it affects ecosystem services.

The purpose of this research is to determine the impact of invasive species particularly water hyacinth (Eichhornia crassipes) on macrophyte and phytoplankton composition, abundance and distribution; and water quality of wetland associated to lake Abaya and to suggest a sustainable management and monitoring strategies.

1.2 Statement of the problem

Although several studies have been made in both Abaya and Chamo lakes, the studies were linked to only to physicochemical properties and the possible pollutant agents assumed to be anthropogenic and environmental factors. They did not give any clue what is happening to biological world in the lakes (Ababu Teklemariam and Bernard, 2004). But evidences showed

4 that the lakes have been affected by invasion by alien species (Firehun Yilma et al., 2012) sediment loading (Alemayehu Hailemicael and Solomon, 2011) and algal blooms (personal observation). Death of fish and other wild animals as a result of water pollution of the lake have been reported (Amha Belay and Wood 1982). There is a shocking report on the others side that Lake Chamo has shrunk by 14.42 % in the last 45 years (Alemayehu Hailemicael and Solomon 2011). This is a possible indicator that the same situation could happen in Lake Abaya since both lakes are found nearly in the same climatic geographic area. They also mentioned that the possible cause is that sedimentation between the Lake Abaya and Lake Chamo by Kulfo River. Both problems i.e. increasing water level and shrinkage of the lake could be a direct consequence of loss of macrophytes. All these problems result in reduction of wetland ecosystem services.

Although the presence of the plant (water hyacinth) was recognized in the study area before 5 years, its ecological importance has not been studied well (Firehun Yilma et al., 2012). No one took step to study the rate of distribution and its impact on local flora and economic activities of the area and to the fates of the lakes at larger scale.

Therefore, this study is conducted to investigate the impact of water hyacinth (Eichhornia crassipes) on composition, abundance and distribution of macrophytes and phytoplanktons and water quality of Lake Abaya wetland.

1.3 Objective of the study

1.3.1 General Objective The main objective of this study was to assess the impact of water hyacinth (Eichhornia crassipes) on composition and abundance of macrophytes, phytoplankton and water quality in Lake Abaya.

1.3.2 Specific objectives 1. To investigate the effect of water hyacinth (Eichhornia crassipes) on the abundance, diversity and composition of macrophytes 2. To determine the effect of water hyacinth(Eichhornia crassipes) on the abundance and composition of phytoplankton 3. To investigate the effect of water hyacinth on water quality parameters. 4. To investigate the impact Eichhornia crassipes on biodiversity of macrophytes

2. LITERATURE REVIEW

2.1 Wetland definition and classification system

According to Ramsar convention (Ramsar Iran 1971) wetlands are defined as: areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six meters (Article 1.1). Article2.1 further explains that it may incorporate riparian and coastal zones adjacent to the wetlands, and islands or bodies of marine water not deeper than six meters at low tide lying within the wetlands. In addition to this different criteria were listed to identify internationally important wetlands and high emphasis is given to ecology type and organisms that it should contain. For example criteria under group B (criteria 3) stated that: A wetland should be considered internationally important if it supports populations of plant and/or animal species important for maintaining the biological diversity of a particular biogeographic region. It remarks that the plant and animals type should be considered in identifying wetland. The Ramsar system of wetland classification identifies 42 types of wetlands which grouped under three main categories. These are inland wetlands; marine or coastal wetlands and human made wetlands. Inland wetlands are water shade regions mainly bounded by land and they are mostly fresh water bodies which are located in inorganic soils. For example Deltas, waterfalls, oxbow lakes and fresh water marshes can be mentioned. Marine/ coastal wetlands found adjacent to oceans and seas. They include water bodies which have depth of less than six meter. They characterized by having high salt concentration. Human made wetlands are wetlands which are created by humans. Aquaculture, ponds, salt exploitation sites, water storage areas and canals are few examples human made wetlands. Few years later United State formulated its own wetland definition and classification system which is called coward classification system. It is consists of five main categories which are called systems. These are the M-marine system, E-estuarine system, R-riverine system, L- lacustrine system and P-palustrine system (Table 1). The classification system has also different modifiers like water regime; different anthropogenic effect; soil type and the most important one is water chemistry. The inclusion of water chemistry in the classification system as wetland modifier is very important thing since water chemistry determines the wetland ecosystem type

6 including the distribution and abundance of the flora and fauna. Anthropogenic effect is also taken in to consideration.

2.2 Role of wetlands

Wetlands are considered as biological supermarkets (USEPA, 1995). This is because they produce a great amount of food that supports a large number of organisms. In this case strong relationship established between organisms. This relationship what we call food web brings great number of organisms together and improves the biodiversity and productivity of the area. Oyedeji and Abowei (2012) also indicated that Aquatic plants including macrophytes determine the productivity of the water body. The major source of this food comes from phytoplankton (Lemlem Sissay, 2003).Wetlands also involved in protection of environmental catastrophes like erosion and flood. Russi et al., (2013) also mentioned this catastrophe is controlled by soil retention ability of wetlands. This of course has dual benefit. In one hand, soil retention will keeps soil fertility and in another case water level of the nearby water body is controlled.

In addition to food supply and flood control wetlands are also a natural home for various organisms. Migratory birds hosted by wetlands, mammals, reptiles and other arthropods dwell in wetland. According to Lemlem Sissay (2003) out of the total number of wild life in Ethiopia, 40 % of mammals and 65 % of birds are found in rift valley wetlands of the country. USEPA 1995 study report indicates that these wetlands serve as breeding site, hunting bush and egg depositing rooms for wild animals. Table 2 below summarizes the major wetland ecosystem services.

Table 1 Major wetland ecosystem services to human benefit

Wetland ecosystem services Benefits to human 1. Provision services  Food  Fresh water  Raw materials  Genetic material 2. Regulating services  Climate regulation  Water flow regulation  Erosion regulation 3. Cultural  Spiritual  recreational value  Aesthetic values  Educational value 4. Supporting services  Sediment retention and accumulation; detoxification of wetland water bodies from heavy metals and other organic residues Source: Millennium Ecosystem Assessment, 2005. Ecosystems and Human-Well-being: Wetlands and Water Synthesis. World Resources Institute, Washington, DC.

2.3 Threats to wetlands

Wetlands are faced with so many challenges. Scholars classify these challenges as Invasive alien species led challenges and Human induced challenges. In the former case since wetlands are the most productive places, they easily attract invasive alien species. Human induced challenges occur as a result of improper utilization of wetland resources and mismanagement of the resources. Lemlem Sissay (2003) has mentioned the major human induced threats like deforestation, encroachment, settlement which occur as a result of population growth, and urbanization. Zelalem Dessalegn (2013) explains how human induced impact affects the quality and quantity of water in Lake Haramaya and Adale leading to loss of biodiversity of phytoplankton, zooplankton, fishes and birds. According to NHWRP (2009) report land

8 fragmentation that occurs as a result of road construction and agriculture has negative impact on wildlife and migratory birds. The fragmentation result in disruption of normal seasonal breeding pattern of some organisms as a result of effect of geographical isolation.

2.4 The consequence of wetlands loss

The major results of wetland loss are disruption ecosystem and decline of ecosystem services (Shibu et al., 2013). As a result of these loss animals will be forced to abandon the area leading to loss of biodiversity. As a result of plant (macrophyte) distraction flooding and erosion occurs; water level of lakes will increase due to sediment loading. The normal hydrological cycling and ground water reserve also affected. Due to loss biodiversity of phytoplankton, fish production decrease as a result the people who live on wetland services economically affected. There is prediction that as a result of land-water interference reduction, there will be a great decline of fish and other crustaceans that dwell at the edge of land and water (Journal of coastal research, 1994).

Figure 3 Production of fish and other crustaceans decline due to shrinkage of wetlands (adapted from Journal of coastal research 1994) Lemlem Sissay (2003) discussed that there are six million people living around Lake Abaya, Chamo, Hawassa and Chew-bahir catchment whose living established on the wetlands. The disruption of these wetlands could unkindly affect the life of all these people. As indicated in the table-1 above all the benefits of the wetland services will be true if and only proper wetland management held on. The death of Lake Haramaya clearly indicates the consequences that result of brutal utilization of the wetland. According to Zelalem Desalegn (2013) report, now the catchment area is being used as grazing land and small scale agricultural practice replacing the indigenous macrophytes. The people of Harari regions had been faced with a problem of potable water as a result of the wetland loss.

2.5 Ethiopian wetland classification system

Based on ecological zone, hydrological function and climatic function the Ethiopian wetlands can be grouped in to four major categories (Leykun Abunie, 2003). 1. Group-I The Afro-tropical wetland system These groups of wetland include western and eastern highlands of the country (figure 3). The average annual rain fall of this area is above 2000mm and it is bimodal type. The wetlands in this biome include: Lake Tana, Hayk, Ashange from the north; Ghibe and Gojjeb from the western highlands. From the eastern highlands Lake Haramaya and swamps of Arsi can also be included (Tilahun et al., 1996) 2. Group-II Somali-Masai wetland system This type of wetland lies along the Great Rift Valley and it includes all lakes which are found in the rift valley. It also includes The Awash river basin from the northern side (Tilahun et al., 1996). 3. Group-III Sudano- Guinean wetland system This type of wetland found in western border of the country (figure 3). Turkana delta, Baro, Beles and Metema and Tekeze river basins are included in this wetland type (Tilahun et al., 1996). 4. Group-IV Sahelian transitional wetland system This type of wetland is found at the north-eastern corner (Afar region) of the country specifically around Dallol depression. This wetland is unique in its kind. The evapotranspiration rate is more than precipitation. As a result drought is commonly happen. Rain fall distribution is unimodal type and not constant. Lake Afambo, Afdera, and Gamari found in this biome (Tilahun et al., 1996).

Figure 4 Map of Ethiopian wetlands, rivers and lakes (from Abebe Yilma) 2.6 Wetlands and water

Understanding the relationship between wetlands and water is a very important step in wetland management and conservation (Russi et al., 2013). All wetlands are established with in water body and along the water basins. The availability and quality of water is maintained by wetlands (Zedler, 2004; Osumo, 2001). The impact of one affects the other. One cannot exist without the other in a natural open environment. Water moves around the earth through its water cycle and wetlands are a crucial part of this path as part of evapotranspiration. Wetlands are not only channels of water cycle but also they absorb and store some of the water to the ground and secure the ground water. They also play a very important role in water treatment (Russi et al., 2013). Waste materials like non-biodegradable trashes, sediments that driven into water during rainy season are checked filtered by wetlands. For these roles they are called “kidneys” of aquatic system. Water; beside its metabolic role in every living organism, it is one of the major criterions for sustainable development. Countries like Ethiopia which is on the stages of development held huge amount of projects including the great renaissance dam, the Omo sugar

12 factory and several other industries which utilize water. So conservation of wetlands secures water supply and sustainable development.

2.7 Vulnerability of wetlands to invasive species

As discussed earlier wetlands are the richest ecosystem in biodiversity and nutrients (Zedler, 2004). They are the storehouses where nutrients and other materials that fled from the terrestrial environment will be placed. Two important conditions can be seen that are causes for vulnerability of wetland ecosystems to invasive species. These are nutrient availability and hydrological disturbance. Based on nutrient gain wetlands can be classified as minerotrophic wetlands and ombrotrophic wetlands (Walter, 2002). The former ones are found at higher nutrient dynamic state. They gain nutrient from outside (surface water through flood) and nutrient can be easily washed away from them. On contrary, ombrotrophic wetlands gain nutrients from precipitation and internal nutrient cycling from their system in a very gradual process. Minerotrophic wetlands usually located at downstream and affected by frequent hydrological disturbance which is promoter of invasion (Julie et al., 2007). These frequent hydrological disturbances create a gap by eliminating some native plants and give opportunity for other alien species to invade the area. The appreciable nutrient availability also attracts invaders to the area. Minerotrophic wetlands can be characterized as a nutrient rich ecosystem but poor in species richness as a result of invasion (Zedler, 2004). Ombrotrophic wetlands are characterized by relatively stable state of nutrient dynamic and low hydrological disturbance and high species richness. As a result they are nutrient poor wetland ecosystem and are not vulnerable to invasion.

2.8 Taxonomy, behaviors, distribution of water hyacinth (Eichhornia crassipes)

Water hyacinth (E. crassipes) was originated in South America, Brazil in Amazon. Then it spread to other regions of America, Asia and African tropical and subtropical regions (Tellez et al., 2006). Water hyacinth is one of the world‟s most invasive aquatic plants (UNEP 2013). According to the UNEP (2013) report water hyacinth is one of the world top ten aggressive invasive plants. Taxonomically the plant is grouped in Angiosperm, in monocots group, in order commelianales in family Pontederaceae (Jafari, 2010; Getachew, 1997). There are two species in the flora region E. crassipes and E. natan (Getachew, 1997). The plant is also grouped as

13 floating aquatic plants. The weed is seen as freely floating plant with simple leaf smooth and shiny cutticular surface and eliptical shape and swelled petiole. The swelled petiole and stem are air filled which enable the plant to be bouant and easily float on the surface of water. The stem of the plant grow horizontally. The flower is aggregated with spike type of inflorescence which consist of 6-10 florets (figure 5). Each floret has zigomorphic type of symmetry with 5-6 basally fused sepals and 5-6 petals tubular with one unique petal. The petals are basally fused. Florets are monocious with 4-5 stamens and one pistill.

Figure 5 Morphology of the flower of water hyacinth (Lake Abaya) Water hyacinth has a fibrour type root system. In favorable condition the plant grows up to 2 meter length but at normal condition it grows with the average height of 40 cm. It has the relative growth rate of 9.34 % and average duplication rate of 7.4 days and with the average biomass of 2.79 Kg/m2 (Guiterez et al., 2001) . The plant also has a rapid sexual replication rate producing 300 propagules at a time from a single seed capsule! The seed can germinate within 2-3 weeks if there is favorable condition or it may remain dormant and viable for 28 years (NWHSP-2012). The growth of the plant is affected by environmental factors. For instance optimum growth occurs in temperature between 25 oC and 27 oC and Tellez et al., (2006) showed that 17 oC to 19 oC is its optimal temperature. But NWHSP (2012) report show that it can tolerate a temperature range 10-35 oC and pH of 4-8. It can survive a salinity level of 5-10 ppt (Cheng, 2005).

2.8.1 Distribution of water hyacinth Water hyacinth was discovered by German naturalist C. von Maritus in Amazon basin 1823 (Gopal, 1987). Then it spread throughout the world. The ability to reproduce both sexually and asexually and its rapid proliferation rate are some of its biological adaptations to spread easily. Its attractiveness with purple color flowers and shiny smooth leaves made people to use it as an ornamental plant. As communication and transportation improved early in 19th and 20th century people carried the plant from place to place across the continent. The Trans-Atlantic triangular trade could have some contribution for the spread of this and other plants from Latin America to Europe and then to Africa. At the end of 20th century the weed already spread throughout tropical and sub-tropical countries from Brazil to Southeast Asia.

In Africa the first invasion of water hyacinth was reported in Egypt in 1879 (Gopal, 1987).Then it spread to Kenya in 1940. In 1998 it was observed in Lake Victoria and reached its maximum (Gichugi et al., 2012). The weed also observed in other African countries like: Zimbabwe in 1937, Mozambique in 1946, Tanzania and Zambia in 1960s and in several other sub Saharan African countries

In Ethiopia the existence of water hyacinth was reported for the first time in 1956 around Koka reservoir and Awash River (Stroud, 1991). Currently it is reported in Gambella area, Aba Samuel reservoir, Matahara Sugar Estate and in Lake Tana (Wondie Zelalem, 2013; Firehun Yilma et al., 2012).

2.8.2 Adverse Impact of water hyacinth on wetland ecosystem

2.8.2.1 Impact of water hyacinth on macrophytes abundance and composition Macrophytes are vascular plants that inhabit wetlands. These plants are capable of living in the area that is permanently or temporarily water logged environment (Bowden et al., 2006). In normal situation, they are the most diverse and stable plant community (Zedler, 2002). They are also exposed to elimination and destruction that probably caused by both humans and invasive alien species. In the presence of for example, invasive species only few macrophytes will survive i.e. invasive plants could affect the vegetation composition and abundance of macrophytes (UNEP 2013; Gichugi et al., 2012; Zedler, 2004).) Report also showed that water hyacinth affect the biodiversity of the area in which it invaded. Water hyacinth and other which have thick mat growth could affect seedling recruitment by blocking seed dispersal (Shibu et al., 2013). Those

15 plants whose seed dispersal is aid by water can be affected by this plant and remain in kidnapped in a certain area. The shading effect of this plant also can affect other plants especially the submerged macrophytes. This fact is also supported by Gichugi et al., (2012). According to their result, water hyacinth affect the occurrence of floating leaved plants i.e. submerged plants like Nymphaea lotus, Ceratophyllum demersum and Najas horrida through shading and competition for nutrients. Water hyacinth is relatively taller than these plants and it has broader leave that can reduce the amount of light beneath its canopy. The fibrous root system of the plant used to with draw nutrients effectively compared to the submerged ones. The allelopathic effect of water hyacinth is also reported by many authors (Chai et al., 2013; Shanab et al., 2010).

2.8.2.2 Impact of water hyacinth on phytoplankton composition and abundance As already mentioned, invasive species have greater impact on aquatic ecosystem. Charles and Dukes (2007) stated that invasive species not only affect ecosystem services but also decrease biodiversity and species extinction. There are so many factors which determine the distribution of phytoplanktons. Light could be the first and basic factors. Phytoplanktons need light to synthesize food. This light should be available in its optimum amount without any interference. However in the presence of some macrophytes like water hyacinth which have broader leaves the light source is not secured for phytoplanktons (Arne, 2013). This results in delocalization of phytoplanktons from macrophyte infested site to another area and resulting in reduction of biodiversity. For those light stress tolerant phytoplanktons another challenges still present competition with other organisms for the same resources. Most invasive species are efficient excellent competent in nutrient utilization. Another factor could be allelopathic impact. There is a report that E. crassipes can excrete growth inhibiting substance like methanolic in water (Chai et al., 2013).

Mironga (2005) studied the effect of water hyacinth infestation on phytoplankton productivity. He conducted controlled experiment and measured the Chlorophyll concentration and dissolved oxygen in infested and non-infested at littoral site. He found that dissolved oxygen and chlorophyll concentration significantly reduced in infested site in the littoral area. However other research which is carried out in Ethiopia; at Lake Tana by Wondie Zelalem (2013) showed that the impact of water hyacinth on water quality, species composition and abundance was less significant. He reasoned out that frequent intervention of invasion helped to reduce the impact.

Probably the location of the lake may have its own contribution. Since Lake Tana is at higher altitude with lower temperature than other rift valley lakes and the behavior of the plant that it is thermophile type reduces its physiological efficiency.

2.8.2.3Impact of water hyacinth on water bio physicochemical property The impact of invasive species on water bio physicochemistry is manifested on the productivity of water. These water quality parameters serve as controlling variables of water. The major controlling variables of water include acidity and alkalinity, Total dissolved solids, pH, Temperature (Eugene, 2013). Other parameters like carbonates sulfides and dissolved oxygen are determined by the change of the above controlling variables. Invasive plants alter the water chemistry in different ways. They put their allelopathic chemical into water and hamper the growth of other organisms or they may take up the available nutrients from it extensively and make other organisms starved (Zedler, 2002).

The amount of oxygen in water is one of the factors that determine water quality. Oxygen level above 7 mg/L is acceptable and recommended for domestic consumption and below 3 mg/L is considered as stress conditions for aquatic organisms (Eugene 2013). The work of Mirogna (2005) in Lake Naivasha shows clearly the possibility of oxygen depletion as a result of dense colony of invasive species. This is probably due to increase in temperature of water due to thick mat of E. crassipes. As the temperature of water increase its Oxygen holding capacity decreases (Eugene, 2013). Another study on Lake Victoria shows that infestation of invasive species like water hyacinth can affect oxygen level. In the same study dissolved oxygen level was increased by 2-4 mg/L after the shedding off the plant from the area (Osumo, 2001). Toft (2000) also showed in his comparative study water hyacinth aggressively snatch Oxygen from water dominating other species.

The water volume of water bodies also can be affected by invasive plants. Invasive plants comparatively have high metabolic activity which made them more competent to the native plans. This high rate of metabolism like photosynthesis and respiration lead them to utilize the available resource like water more rapidly. Calvert (1997) in his study stated that the rate of evapotranspiration of water from the surface of infested sites is 1.8 times faster than non-infested sites. Invasive plant species like E. crassipes could have even faster than this figure because of larger leaf area (Charles and Dukes, 2007). Jack (2005) also explained that this high

17 evapotranspiration rate result in reduction in water level and high concentration of salts and other toxic chemicals. This in turn has an impact on salinity of water. Shrinkages and drying out of lakes and other small water ponds which do not have a constant inflow of water throughout the year might be affected by such problem.

Water hyacinth also affects water clarity. Water turbidity can be defined as the degree of water body to allow light to pass through it. Turbidity can be caused by TSS (Total Suspended Solids). There is direct relation between Turbidity and TSS (Table 2). TSS has its components TFSS and TVSS (Total Fixed Suspended Solids and Total Volatile Suspended Solids). It is clearly unknown that which component has more direct impact on water clarity. But one thing is clear that the former one is caused by physical feature of the water body and it is mainly consists of clay and other non-dissolved inorganic particles and the later one occurs as a result of biological entities(derbies of planktons). Studies show that there is inverse relationship between the abundance of aquatic weeds and water turbidity (Salvic, 2007). It is estimated that less than 30% weed coverage of the total surface of water will not affect water clarity.

Table 2Total suspended concentration estimated from turbidity measurement

Water parameters Measured values

Turbidity 2 5 10 20 50

TSS due to soil sediment 2.2 6.3 12 24 64

TSS due to algae 2.2 4.7 10 36 54

Source: Eugene R. Weiner (2007)

Both TDS and salinity indicates the amount of dissolved salts in a given water sample and conductivity is directly related to TDS (Eugene, 2007). TDS value less than 1200 mg/L is generally acceptable. If the TDS value falls between 1000-3000 mg/L the water is taken as slightly saline and if it‟s between 10 000-35 000 mg/L very saline and not suitable for most organisms. Water hyacinth sites have lower salinity and conductivity measurement. This may be due to that water hyacinth has withdrawal ability of some salts from the water and store in its cell sap. Yapoga (2013) indicated that water hyacinth can take up salts of Zn, Cu, Cd, Cr from water.

2.8.2.4 Impact of invasive species on ecosystem services Ecosystem services are benefits provided to human society by natural ecosystems (Charles and Dukes, 2007). These services occurred as the results of ecosystem processing. These services are bases on which the life of humans and other organisms established and maintained. But the gain from such services is not consistent and is affected by several factors like human activities, climate change and invasion. Invasive species have several impacts on ecosystem services. Charles and Dukes (2007) showed that invasive species are responsible for alteration of ecosystem and ecosystem services. They made intensive study on how effect of invasive species is linked to community dynamics and ecosystem process to put influence on ecosystem services. They suggested that the impact which is caused by invasive species is not only on a single service but rather has a cascade effect and complex so that the assessment impact of invasive species should be viewed in multi direction. For instance the impact of water hyacinth on phytoplankton results in reduction of fish production in the area. This in turn create stress on fish stock on the market leading to food shortage; economic problems for customers (Kateregga and Sterner, 2008). The following concept map (figure 6) illustrates the cascading effect relationship

19 ofwater hyacinth on wetland ecosystem.

Figure 6 Cascading effect of water hyacinth (adapted from Julien, M.H., 199)

Toft (2000) also mentioned that biological invaders can alter population dynamics and community structure of the native ecosystem. This in turn affects the biodiversity of the ecosystem. Julie et al (2007) also discussed that alien species can affect the area by producing hybrid vigor that much more competent than the native plant but that has trait resemblance much more to the alien than its parents. This causes speciation that result in incompatibility with native partner for successful reproduction and finally leading to locally extinction. Tellez (2008) raised another issue that in studying invasive species and their distribution, it is important to consider geobotanical and chronological perspective. He suggested that with the aid of these tools it is possible to predict the reproductive potential of invaders on the basis of water physicochemical parameters. For instance, high growth rate of water hyacinth observed during summer season. Tropical regions are more favorable than temperate regions for rapid plant proliferation rate this

20 is because these regions are hotter and relatively have longer photoperiod throughout the year. The work of Osumo (2001) strengthen the above facts clearley.

2.8.3 Beneficial impact of water hyacinth Wetland invasive plants are beneficial in certain condition. Few studies indicated that some plants which are internationally considered as horrific invasive weeds are found to be used as remedies for some ecological problem. For instance, Jafari (2010) in his research indicated the use biotic purifiers to waste water treatment. He indicated that plants like water hyacinth have the potential role in waste water treatment. Similarly another study proved that E. crassipes can serve as phytoremediation plant in cleaning up some heavy metals from industrial waste water (Yapoga et al., 2013). In their study the plant found to be high bio accumulator for toxic heavy metals Zn, Cd, Cu and Cr and the root of the plant accumulated more than the leaves.

Another application of water hyacinth is indicated by Offer and Iyagba (2013) that it also used in soil fertility improvement. These two persons conducted impressive experiment on biostimulative effect of water hyacinth on the germination of okra plant (Abelmochus esculentus) on petroleum contaminated soil. They found that the soil amended with water hyacinth showed 6.6, 25.3 and 48.7% increase in seed germination. Jafari (2010) also discussed that water hyacinth is used as fertilizer. The plant mulch and green manure can be directly applied after decomposition of the tissue as compost. These could be alternative solutions for farmers of developing countries which cannot get modern fertilizer that costs more than their crops.

Another application is in the area of alternative energy sources. Jafari (2010) discussed that water hyacinth can also be used as biogas production. Prachayasittikul et al (2007) were able to produce ethanol from water hyacinth plant. Their finding showed the future hope and prospectus for energy production from cheap and easily growing plants. This finding has its own global solution for food crisis. It minimizes food shortage by substituting some human food stuff that were being used as biofuel to feed vehicles rather than feeding starved people.

Water hyacinth also used as animal fodder. Jafari (2010) in his report indicated that the possibility of using the plant as animal feed since the plant constitute some essential nutrients that can be utilized by ruminant and other animals. However if the plant is harvested from waste water treatment area it could be toxic in harboring some heavy metals in its tissue.

Beside this water hyacinth has been used to make semi-industrial and household articles like rope, basketry, mats, and bags and so on in countries like Philippines, Indonesia and India (UNEP, 2013). This is a very important opportunity with regard to creating jobs for some people who have low income in developing countries.

3. MATERIALS AND METHODS

3.1 Description of study area

3.1.1 Location of the study area

The study was conducted at the western side of Lake Abaya. Lake Abaya is one of Rift Valley lakes found in southern Ethiopia Gamo Gofa Zone in Arba Minch. It is the second largest lake next to Lake Tana in the country. It is located between 5o55′ 9′′ N to 6o35′30′′ N latitude and 37o 36′ 90′′ E to 38o 03′ 45′′ E longitude (figure 6 and 7). The lake including the islands has a total area of 1108.9km2 (Seleshi Bekele, 2007). It has the longest length of 79.2 km2 and with the maximum width of 27.1 km. the mean and the maximum depth is 8.6 m and 24.5 m respectively (Arne, 2013). It is located at an average altitude of 1,235 meter above sea level (Seleshi Bekele, 2007).

Figure 7 Map of Ethiopia showing location of the study area

Figure 8 Landsat satellite image showing location of sampling sites of the study area

3.1.2 Climate

Based on ten years climate data, (2001-2010), Lake Abaya basin expersence a bimodal rainfall pattern (figure 8). It has an average annual temperature of 22.9 oC and an average rainfall of 768 mm. The rainy season of the study area ranges from March up to November with mean minimum monthly rainfall is in January and maximum in May. Hot and dry season is prominent from December to February. The mean minimum daily temperature of the coldest month and the mean maximum temperature of the warmest months are 15.0oC and 32. oC respectively.

Figure 9 Climadiagram of the study area (from 2001-2010)

3.1.3 Plant and animals life of the study area

Despite its size wider than Lake Chamo, Lake Abaya has lower productivity in fish yield. Several mammals, fishes, birds and reptiles live along the shore. Macrophytes like cattail, commelina, water lettuce and various type of unidentified plants found around the lake.

3.1.4 Population and socioeconomic condition

The population of the study area is estimated to be 2,300 (CSA, 2005). The people are engaged mainly with fishery and small scale agricultural practices. Besides for domestic services, the lake serves as means of transportation, fishery and tourism for local people.

3.2 Design of the study area

The study was carried out in south western side of the lake (figure 7). This is the site where the invasive plant located and easily reachable. The total area under the study coved is about 1.50 kms2. To study the distribution of the plants, four sampling areas at the shore were selected and marked with the aid of GPS (Garmin model eTrex) and were marked as site-1, site-2, site-3 and site-4. The locations were purposely selected from the area where mass growth of the plant is found and area where no growth the plant observed. Site-1 and site-3 were infested sites and site- 2 and site-4 were non-infested sites. Belt transect which is two dimensional transect was made at each site along edge of the lake.

3.3 Data collection

3.3.1 Macrophyte data collection

Using systematic methods of sampling, plants were collected and identified from the selected sites and the species abundance and richness was assessed from the selected sites to determine the impact of invasive species on the abundance of other macrophytes. Plant distribution and abundance was studied along the belt transects. A belt transect was laid along the side of the lake. Sampling points with 0.5 X 0.5 m2 quadrats was marked along the belt transect 25 meter a part from each other (Schimid, 1965). A total of 60 quadrats 15 from each site were studied. Then species identification was carried out using expert methods and Flora of Ethiopia and Eritrea was used as an aid. On field observation macrophytes were counted within each plot.

3.3.2 Phytoplankton data collection

To estimate the abundance of planktons, water sample with the volume of 2 liter with opaque plastic bottle was taken and filtered with 10µm pore size nylon mesh and preserved with 4% luglo‟s solution (100gm of potassium Iodide dissolved in 1000ml of distilled water and then add 50 g of crystalline Iodine to the solution. Then 100ml glacial acetic acid was added to the mixture) with a ratio of 1 ml to 1000 ml sample water and stored at 4oC refrigerator.

3.3.3 Water quality data collection In parallel to data collection for macrophytes and phytoplanktons, some water quality parameters were measured in the field. From each sampling plots two litter of water was drawin with two replicates one from the surface and the other from subsurface at possible sacci disck reading point by using core sampler.

3.4 Data analyses

3.4.1 Macrophyte distribution and abundance data analyses

For macrophytes species richness, abundance and Simpson‟s diversity index was analyzed using appropriate formula. Using SPSS version 17 Multiple Correspondence Analyses with two Dimensions was computed. Degree of the invasive infestation verses species abundance for macrophytes correlation was computed Using Ms-Excel. Analyses of variance for some water quality parameters within the plots with respect to four sites were computed Using SPSS, abundance, proportion(relative density), density, dominance of species were calculated. In addition simpson diversity index (D), evenness, richness and similarity index of the plots calculated using appropriate formula(Adrian, 2006).

Abundance(A) (Eq.1)

Proportion(P) (Eq.2)

Relative density(R) (Eq.3)

Dominance (Eq.4)

(Eq.5)

Evenness = (Eq.6)

Richness=(Dmg)= (Eq.7)

Where: N=total number of organisms; n=number of particular species; s=toal number of spp

Sorensen index = ; A-the nuber of species in in community „A‟ (Eq.8)

B- the number of species in community „B‟ C- the number of common species in both community

3.4.2 Phytoplankton distribution and abundance data analyses

In laboratory microscopic analysis was made within 24 hrs. To determine the abundance of plankton 1 mL of the sample was place on counting chamber and was observed under inverted microscope with 40X magnification (Pirner, 2005). Then total cellular organism was computed using:

No of cells per mL (Eq.9)

Dilution factor= (Eq.10)

3.4.2.1 Waterbio physicochemical property analyses

3.4.2.2 Chlorophyll-a measurement

Chlorophyll-a measurement is used as indicator for the amount of productivity of the lake. Chlorophyll concentration at In vitro condition was measured by using flicker Aqua florometer (RS-163, Belgium) device. Water sample was taken from surface and sub-subsurface at each sampling points. The chlorophyll sample and turbidity reading was taken from infested and non- infested sites on the field. Chlorophyll-a concentration (uncorrected for phaeopigments) was

29 estimated by taking 200-500 mL aliquots of water sample. The sample was filtered through Whatman glass microfiber filter papers. The filters was wrapped in labeled aluminum foils and transported to the laboratory in an ice box. Algal seston was ground manually with a glass rod and Chlorophyll a (Chl-a) was extracted using 90% cold acetone. The algal material was centrifuged at 4000 rpm for 5 minutes. The absorbance of the centrifuged extract was measured at 665 and 750 nm using a spectrophotometer (UV/VIS spectrophotometer RS-295 model, India). Sample treatment was made according to Wetzel and Likens (2000) and calculation of Chl-a concentration was done using the following formula (Talling and Driver, 1963).

⁄ (Eq.11)

Where; E665 and E750 are absorbance at 665nm and 750nm, respectively. Ve = Volume of extract in ml Vf = Volume of sample filtered in liter Z= Path length of the cuvette (1cm)

3.4.2.3 Dissolved oxygen and other parameters

The dissolved oxygen, salinity, conductivity and PH of the selected sites infested with the weed and non-infested sites was measured simultaneously with other parameters like chl-a concentration at the mid of every month for three continuous months from July 15th to Sept 15th. Environmental multi-meter Hatch (model 40d, India) was used to measure the in-vitro condition of the above parameters of the sites with various depths with possible secchi-disk reading point.

4. RESULTS AND DISCUSSION 4.1 Abundance, composition and distribution of macrophytes

A total of 23macrophytesspecies belonging to 15 families were observed from the study sites. Out of these 16(69.5%) of the species were observed in the infested sites whereas 17(73.9%) of the total were observed in non-infested sites. Two families, namely Cyperaceae and Poaceae constitute of which take 40% and 26.6% of the total observed families respectively (Table 3). Seven plant species from family Araceae, Polygonaceae, Potamogetonaceae, Alismaceae, Sparginaceae and Cyperaceae are observed only innon-infested sites. Five species namely Bacopa monnieri, Bulbine abyssinica, Echinochloa robtundiflora, Isoetes, Leptochloa fusca were found only in infested sites. The remaining plant species mainly from poaceae and cyperaceae family were found to be common in both infested and non-infested sites. Table 3 Total Macrophytes records in four sites species name Family habit *category Inf Noinf Bacopa monnieri Scrophulariaceae Herb Sm  X Bulbine abyssinica Aspodelaceae shrub Em  X Commelina diffusa Commelinaceae Herb Sm   Costus lucanusianus Costaceae shrub Em   Cynodon dactylon Poaceae Forb Sm   Cynodon plectostachyus(belatte) Poaceae Forb Sm   Cyperus difformis Cyperaceae Herb Em   Cyperus dives Cyperaceae Herb Em   Cyperus esculentus Cyperaceae Herb Em X  Eichhornia. crassipes pontederaceae Herb FF  X Echinochloa rotundiflora Poaceae Forb Em  X Eleocharis obtusa Cyperaceae Herb Em   Isoetes Isoetaceae Herb FF  X Lemna aequinoctialis Lemnaceae Herb FF X  Leptochloa fusca Poacea Forb Sm  X Pistia stratoides(water lettuce) Araceae Herb FF X  Polygonum punctatum Polygonaceae Herb Em X  Potamogeton crispus Potamogetonaceae Herb FF X  Rhynchospora corymbosa Cyperaceae Forb Em   Sagittaria latifolia Alismaceae Herb Em X  Schoenoplectus corymbosa Cyperaceae Herb Em   Spharganium americanum Sparginaceae Herb Em X  Typha latifolia Typhaceae Herb Em  

*Under category FF=free floating, Em=emergent, Sm= submerged, =present, X= absent

Concerning plant category, 13 out of 23 (56.5%) were emergent, 5 (21.7%) were submerged and the remaining 5 (21.7%) were free floating ones (figure 11).

Free floating d e m o d e m o d e m o d e m o Emergentd e m o Submerged

d e m o d e m o d e m o21.74%d e m o d e m o

d e m o d e m o d e m o d e m o d e m o 21.74%

d e m o d e m o d e m o d e m o d e m o

d e m o d e m o d e m o d e m o d e m o 56.52%

d e m o d e m o d e m o d e m o d e m o

Figure 10 Plant distribution based on different category types in study area

Eleven species were recorded from site-1 (infested site) and E. crassipes being the most, dominant and with the highest density followed by Cynodon plectostachys and Cypress difformis in descending order whereas C. diffusa, B. abyssinica and E. rotundiflora took lower position rank in the area (Table 4).Even though some macrophytes have a considerable abundance, they were only restricted to certain plots. For example, C. plectostachys appeared only in 8 plots whereas E. Crassipes was highly distributed occupying the whole 15 plots. All macrophytes except Costus lucanusianus with two digit individuals abundance seems to co-exist with E. crassipes. But C. lucanusianus only limited within 3 plots.

Table 4 Macrophyte distribution status in site-1

total Observed Abundanc Relative Dominanc Site-1 indv plot e propn Density e Eichhornia crassipes 75 15 5.00 0.43 42.61 1.00 Cynodon plectostachyus 19 8 2.38 0.11 10.80 0.53 Cyperus dives 15 7 2.14 0.09 8.52 0.47 Cyperus difformis 14 7 0.52 0.08 7.95 0.47 Cynodon dactylon 13 7 1.86 0.07 7.39 0.47 Costus lucanusianus 12 3 4.00 0.07 6.82 0.20 Typha latipholia 10 6 1.67 0.06 5.68 0.40 Schoenoplectus corymbosus 6 3 2.00 0.03 3.41 0.20 Echinochloa rotundiflora 5 3 1.67 0.03 2.84 0.20 Bulbine abyssinica 4 2 2.00 0.02 2.27 0.13 Commelina diffusa 3 2 1.50 0.02 1.70 0.13 176 1.00 100.00

In site-3 (infested sites), 11 species were recorded among which E. crassipes and Typha latifolia were the most frequently observed species (Table 5) and only the two species took above 50% proportion over the rest. Here again Typha latipholia has number of individual over nine plots. But remaining nine species are highly dominated and remained in restricted plots. Isoetes seems the most abundant species but the relative density and dominance analyses of the community showed that it is one of rare species in the study site.

Table 5 Macrophyte distribution status in site-3

Total Observe Relative Site3 idvd d plots Abund Propn density Dominance Eichhornia crassipes 34 12 2.83 0.38 37.78 0.80 Typha latifolia 18 9 2.00 0.20 20.00 0.60 Bacopa monnieri 10 4 2.50 0.11 11.11 0.27 Cynodon plectostachyus 5 4 1.25 0.06 5.56 0.27 Cyperus difformis 5 4 1.25 0.06 5.56 0.27 Schoenoplectus corymbosus 5 4 1.25 0.06 5.56 0.27 Cynodon dactylon 4 2 2.00 0.04 4.44 0.13 Eleocharis obtuse 3 3 1.00 0.03 3.33 0.20 Isoetes 3 1 3.00 0.03 3.33 0.07 Rhynchospora corymbosa 2 2 1.00 0.02 2.22 0.13 Leptochloa fusca 1 1 1.00 0.01 1.11 0.07 90 1.00 100.00

In site-2 (non-infested site), fourteen macrophyte species were recorded (Table 6). C. plectostachyus followed by C. esculentus, and cynodon dactylon were the most abundant macrophytes. Polygonum punctatum and Lemna aequinoctialis have good number of individuals but were recorded in less than ten plots. C. lucanusianus, S. americanum and S. latifolia were the least abundant species. Similarly regarding the relative density and dominance, C. plectostachyus, Eleocharis obtusa and Isoetes were at higher rank respectively whereas Rhynchospora corymbosa and Sagitaria latifolia in the lower rank.

Figure 11 Partial view of water hyacinth infested site in the study area

Table 6 Macrophyte records from site-2 (non-infested sites)

total sampled Relative site-2 indv plots Abundance prop density Dominance Cynodon plectostachyus(belatte) 65 15 4.33 0.26 25.69 1.00 Eleocharis obtusa 29 11 2.64 0.11 11.46 0.73 Isoetes 21 10 2.10 0.08 8.30 0.67 Polygonum punctatum 19 8 2.38 0.08 7.51 0.53 Lemna aequinoctialis 18 9 2.00 0.07 7.11 0.60 Cyperus esculentus 17 6 2.83 0.07 6.72 0.40 Potamogeton crispus 15 8 1.88 0.06 5.93 0.53 Cynodon dactylon 14 8 1.75 0.06 5.53 0.53 Schoenoplectus corymbosus 14 7 2.00 0.06 5.53 0.47 Spharganium americanum 14 9 1.56 0.06 5.53 0.60 Costus lucanusianus 11 8 1.38 0.04 4.35 0.53 Pistia stratoides 8 5 1.60 0.03 3.16 0.33 Rhynchospora corymbosa 6 3 2.00 0.02 2.37 0.20 Sagittaria latifolia 2 2 1.00 0.007 0.79 0.13 253 1.00 100.00 In site-4 (non-infested sites),13 species were recorded among which C. plectostachys , S. corymbosa and C. difformis were the most abundant species and R. corymbosa, P. punuctatum and R. corymbosa rarely observed species (Table 7). Even though R. corymbosa and S. latifolia seems to have higher abundance value, the relative density and dominance value clearly indicated that they were the least frequently observed plants.

Table 7 Macrophyte records from distribution site-4

Total observed Relative Site-4 indv plots Abund Prop Density Dominance Cynodon plectostachis 31 7 4.43 0.17 16.85 0.47 Schoenoplectus corymbosus 30 10 3.00 0.16 16.30 0.67 Cyperus difformis 25 11 2.27 0.14 13.59 0.73 Cyperus dives 18 5 3.60 0.10 9.78 0.33 Cynodon dactylon 17 6 2.83 0.09 9.24 0.40 Eleocharis obtuse 16 7 2.29 0.09 8.70 0.47 Lemna aequinoctalis 13 7 1.86 0.07 7.07 0.47 Commelina diffusa 9 5 1.80 0.05 4.89 0.33 Pistia stratoides(water lettuce) 8 3 2.67 0.04 4.35 0.20 Sagittaria latifolia 6 2 3.00 0.03 3.26 0.13 Polygonum punctatum 5 2 2.50 0.03 2.72 0.13 Rhynchospora corymbosa 3 1 3.00 0.02 1.63 0.07 181 1.00 100.00

As it can be seen from the above result, E. crassipes was the most dominant species in two of the study sites. Site-3 is the most affected sites with invasion of E. crassipes. As the result it has the lowest species composition and total number of individuals. Even though the species number is comparable to site-1, the total numbers of individuals are less than site-1.The proportion analyses showed that the ratio of water hyacinth over the other macrophytes is 0.43 and 0.38 in site 1 and site 2 respectively. This indicates that how the area is monopolized by a single species. This finding also agree with UNEP (2013) that E. crassipes can dominate other macrophytes colonize the area it invaded independently.

In the present study Pistia stratiodes was observed only in 5 plots of non-infested sites. Arille (2011) discussed the reason for such kind of situation that E. crassipes out competes other macrophytes like P. stratiodes for available nutrients. This is why P. stratiodes probably not observed in both infested sites. Isoetes is submerged macrophyte which was affected by shortage of light. Most likely the thick mat growth of E. crassipes in site-1 affected the growth of Isoetes. It was found in numerous amounts in site-2 where there is no influence. It appeared again in less amount in site-3 where the alien present comparatively in lower number. This is probably due to the fact that submerged plants are more affected than emergent macrophytes plants for shortage of light which is caused by the shading effect of invasive species that result in less photosynthesis activity (Gichugi et al., 2012). The current study also confirmed this fact that the abundance of emergent macrophytes is almost more than twice the submerged ones (figure 11).

As shown in (figure 12), T. latifolia has a comparable number of individual and it seems to co- exist with the dominant plant. Tellez (2008) in his report indicated that T. latifolia is a beneficial plant for the alien species as mechanical supporter during early growth stage. In another case, C. plectostachys seems to be competing with E. crassipes. More growth of one observed in the less occurrence of the other. For instance in site-1 (infested site) the number of C. plectostachys is 19 and E. crassipes with 75 individuals (Table 4) but in site-2 (non-infested sites) the number of C. plectostachys increased to 65 (Table 6). However in site-3(infested site) the number of E. crassipes reduced by half in the presence of only 5 individuals of C. plectostachys (Table 5). Similarly in site-4 (non-infested site) C. plectostachys seems that it is recovered and increased to 31 individuals.

The number of species for other macrophytes with degree of infestation of water hyacinth has also showed significant corelationat r = 0.904 pearson correlation. As the number of water hyacinth per plot increases the species number for other macrophytes decrease (figure 13). This shows that E. crassipess is replacing the rest of the species. Arille (2011) and Tellez (2008) also reported that a similar situation could happen when invasive species colonize wetland and floral diversity is highly affected. Gichugi et al., (2012) showed that the succession of water hyacinth and other related allien species affect the abundance and diversity of macrophytes which resulting into monotypic structure.

10 y = -1.4839x + 11.928 R² = 0.818

5 perplot

0 1 2 3 4 5 6 7 8 numberofother species Number of water hyacinth per plot

Figure 12 Number of species versus water hyacinth spatial distribution Similarity index of study sites (Beta diversity)

The similarity of the four sites interms of species composition computed by using Sorensen (1948) was given in Table 8. Site-1 with site-2 and site-2 with site-3 show less similarity than other pairs of sites. Site-2 with site-4 shows more similarity than the other pairs because they are uninfested sites.

Table 8Sorensen similarity index of the four study sites (beta diversity)

Site-1 Site-2 Site-3 Site-4 Site-1 1 0.4 0.45 0.58 Site-2 1 0.4 0.66 Site-3 1 0.58 Site-4 1

Site-1 and site-3 are the most disturbed sites due to the alien species. The species abundance of site1 and site-3 is lower than the other sites but for unknown reason they are less similar. But as the species compostion of two adjecent community is high, they have more chance to have plant species in common and to be more similar since similarity index is dependant up on the number of common species between the two communities.

The species richness index is done based on individual-based sampling technique (Adrian, 2006). The species richness index showed that water hyacinth infested sites (1and 3) were relatively poor in species composition (Table 9). Higher Simpson index (D) values in site-1 and 3 also additionally showed that the observed plots have lower diversity that have been occupied by invassive species. Further more, the species evenness of the four sites indicated that infested sites have relatively lower evenness index than non-infested sites which is an indicator of the diversity status of the area dominated by water hyacinth.

Table 9 Macrophyte diversity, evenness and richness in four study sites

site D(Simpson’s index) Evenness Richness 1 0.22 0.40 1.93 2 0.11 0.60 2.35

3 0.20 0.43 2.22 4 0.11 0.67 2.13

The ANOVA analyses result (Table 10) showed that there is significant variation of the above results at alpha =0.05 level.

Table 10 Diversity, evenness and richness variation among study sites

Sum of Squares df Mean Square F Sig. Simpson’s index Between Groups .011 3 .004 . . Within Groups .000 0 . Total .011 3 evenness Between Groups .050 3 .017 . . Within Groups .000 0 . Total .050 3 richness Between Groups .093 3 .031 . . Within Groups .000 0 . Total .093 3 UNIANOVA site BY smindex evenness richness /METHOD=SSTYPE(3) /INTERCEPT=INCLUDE /CRITERIA=ALPHA(0.05) /DESIGN=smindex evenness richness smindex*evenness smindex*richness evenness*richness smindex*evenness*richness.

4.2 Distribution and abundance phytoplankton

A total of 30 genera of phytoplanktons were recorded in all study sites (Table 11). Among these 16 genera (53.3 % of the total records) in five families were from non-infested sites (figure 14). These include: Bacillariophyceae, Chlorophyceae, Cyanophyceae, Dinophyceae and Euglenophyceae. This distribution at family level is similar to Lake Adale and other related Rift Valley Lakes (Zelalem Dessalegn, 2013). Which he reported that Chlorophyceae, Cyanophyceae, Bacillariophyceae, Dinophyceae and Euglenophyceae were frequently observed. However, in terms of abundance it is lower than the mentioned lakes (Nebeyu Mohamed, 2009). According to Nebeyu, 50 species were found and Chlorophyceae were the most dominant families followed by cyanophyceae in Lake kuriftu. In infested sites, the record was further reduced by 46.6% and 14 “individuals”or genera were observed. In infested sites only three families were recorded (figure 14). These families include Cyanophyceae, Bacillariophyceae and Chlorophyceae.

Table 11 Phytoplankton in water hyacinth infested sites and non-infested sites

Abundance (cell/litter) Genera Infested sites Non infested sites Family

Actinella Bacillariophyceae 200 NR Anabaena Cyanophyceae NR 120 Chlorogonium* Chlorophyceae 520 NR Phacus Euglenophyceae NR 240 Chrococcus Cyanophyceae 200 NR Closterium Chlorophyceae NR 360 Closteriumacerosum Chlorophyceae 120 NR Closteriumarcherianum Chlorophyceae 40 NR Coelastrum Chlorophyceae NR 80 Coelospharium Cyanophyceae NR 120 Cosmarium Chlorophyceae NR 80 cyanoptyche Cyanophyceae 40 NR Cyclotella Bacillariophyceae 520 NR Dactylococcopsis Cyanophyceae 120 NR Entophysalis Cyanophyceae 30 NR Euastrum* Chlorophyceae NR Rare Gleocapsa Cyanophyceae NR 80 Gomphonyma* Bacillariophyceae NR Rare Gonium Chlorophyceae NR 80 Hydrocera Bacillariophyceae NR 40 Micratrias Chlorophyceae NR 40 Microcoleus Cyanophyceae NR 480 microcyst Cyanophyceae Rare 680 Nostoc Cyanophyceae NR 120 Oocyst Chlorophyceae NR 160 Ooedogonium* Chlorophyceae NR Rare Peridium Diniphyceae NR 160 Raphidiopsis Cyanophyceae 40 NR stephanodiscus Cyanophyceae 80 NR Surirella Bacillariophyceae 160 NR surirella patella Bacillariophyceae 200 NR Volvox Chlorophyceae NR 80

This shows that how the invasive plant affect the abundance and distribution of the phytoplanktons. Sanaa et al., (2010) and Shanab et al., (2010) reported that water hyacinth has some allelopathic substance that hinders the growth of Oocyst and gonium from green microalgae and Microcyst, Nostoc and Gleocapsa from Cyanobacteria group. The other speculation is that since non infested sites contains large number of phytoplanktons, there will be also a balanced number of predators (zooplanktons) relatively in more abundance than in infested sites (Erne, 2013). To escape from these predators majority of phytoplanktons in non- infested sites were colonial forms. The formation of colony is an adaptation to avoidance of predators. The bigger size they are, more and resistant to predation (Lurling et al., 1997). In non- infested sites family Chlorophyceae was the most abundant but in infested site Cyanophyceae is the most abundant family (figure 14). This is similar to Brendnock et al., (2003) results. At genera level microcyst (from Cyanophyceae family) which is one of nuisance Cyanobacteria is found to be the most abundant in non-infested site. But in infested sites microcysts were less frequently observed (Table 9).

Families in Non-infested sites 10 d e m o d e m o d e m o Commond e m o familiesd e in m o both sites Families in infested sites

8 d e m o d e m o d e m o d e m o d e m o )

6 d e m o d e m o d e m o d e m o d e m o

cell/litter (

4 d e m o d e m o d e m o d e m o d e m o

Abundance Abundance d e m o d e m o d e m o d e m o d e m o 2

0 Chlorophyceae Cyanophyceae Bacillarophyceae Dinophyceae Euglenophyceae Families

Figure 13 Phytoplankton abundance distribution at family level between infested and non- infested site

Closterium and Phacus found in both sites. This is because Closterium can survive in shady dry area for a prolonged period of time and when situation improved, it can photosynthesize like as

41 any other open water algae (Brook and Williamson, 1988) and phacus and other related Euglenophyceae groups have locomotory structure flagella that enable them to move to light accessible area and back to the area to escape from predators. Euastrum, Gomphonyma and Oedogonium which belongs to Chlorophyceae and Bacillariophyceae families found to be rare and only observed in non-infested sites. This is because most algae from these families are highly dependent up on light for their active functioning of chlorophyll and probably they cannot tolerate the shading effect of water hyacinth.

The distribution of phytoplankton also shows variation between sites (spatial variation). As can be seen from the figure 15, relatively lower distribution of Chlorophyceae observed in site-1 and 3 (infested sites) but higher in site-2 and 4(non-infested sites). Similarly Euglenophyceae and Dinophyceae follow the same trend. However the distribution and abundance of Bacillariophyceae and Cyanophyceaeis higher in infested sites but lower in non-infested sites. This most likely indicated that Cynaophyceae and other related groups can survive in anoxic and light stress condition, which is created by the high mat growth of E. crassipes, while other photoautotrophic driven off (Nebeyu Mohamed, 2009). Cyanophyceae also have N-fixing ability which works in anoxic condition. This is beneficial for water hyacinth to establish symbiotic relationship with such groups to satisfy its N-demand in such nutrient poor environment (Tellez, 2008).

10 9 8 chlorophysicae 7 6 bcillariophyceae 5 cyanophyceae 4 Abundance 3 euglenophyceae 2 diniphyceae 1 0 site-1 site-2 site-3 site-4

Figure 14 Phytoplankton distribution (at family level) between infested and non-infested sites

4.2 Water bio physicochemical parameter measurements

Table 12 Water bio physicochemical property distribution

Site-1 Site-2 Site-3 Site-4 Parameters N Mean StdEr Mean StdEr Mean StdEr Mean StdEr

Turb (NTU) 15 22.3 0.32 125.7 0.59 22.48 0.48 131.28 0.02 Chl-a (mg/L) 15 105.9 0.72 243.8 0.29 110.52 1.01 265.19 0.10

DO (mg/L) 15 2.6 0.09 6.7 0.01 3.16 0.07 6.59 0.03 Temp (oC) 15 28.3 0.02 24.7 0.01 27.8 0.04 24.6 0.03 TDS (mg/L) 15 533.9 0.37 963.8 0.86 539.73 0.80 896.44 0.74 PH 15 8.6 0.00 8.5 0.01 8.53 0.01 8.51 0.01 Sal (ppt) 15 0.8 0.02 0.9 0.01 0.94 0.01 0.94 0.01 Cond (µS/cm) 15 874.0 0.51 944.2 0.49 883.01 0.44 958.66 1.27

TSS (mg/L) 15 235.8 1.20 373.2 0.53 294.31 0.61 411.25 1.24 StdEr= standard Error, Turb=Turbidity, Chl-a=Chlorophyll-a, DO=Dissolved Oxygen, Temp=Temperature, TDS=Total Dissolved Solids, Sal= Salinity, Cond= Conductivity, TSS= Total Suspended Solids…..

Turbidity of water in infested site-1 and site-3 found to be 22.38±0.32 and 22.48±0.48 NTU respectively (Table 12 and Appendix 2 and 3) which is lower than non-infested sites (Table 12). In non-infested site-2 and site-4 it was found to be 125.76±0.59 and 131.28±0.02 NTU respectively (Table 12). As indicated in Appendix 2 and 3, site 1 and site 3 have lower turbidity records than the non-infested sites (2) and (4). This clearly showed that water hyacinth has negative impact on turbidity of water. The Turbidity of water is normally occurs due to the presence of other smaller macrophytes, phytoplanktons, zooplanktons and inorganic substance like clay and silts. When reduction of number of these organisms occurs as a result of competitive exclusion principle (Hardin, 1960) due to effect of water hyacinth, it results in lower turbidity (Mirogna, 2005). In terms of food chain, water hyacinth traps organic detritus that can

43 be used as food by other organisms. This leads to reduction of the heterotrops (zooplanktons and other macro invertebrates) which are responsible for higher turbidity of water (Mirogna et al., 2012). The concentration of chlorophyll-a also found to be 105.96±0.72 and 110.52±1.01 site-1and3 respectively (Table 12) which is again lower than non-infested sites (Appendix 2 and 3). But in non-infested sites 243.85±0.29 and 265.19±0.10 were recorded in site-2 and 4 respectively. The current result also agrees with many other findings (Tellez et al, 2008; Gichugi et al., 2005; Mirogna, 2005). This may be due to the fact that water hyacinth foliar coverage may reduce light penetration to alga in the lake disabling them to produce chl-a (Mirogna, 2005). Other studies in other places however showed that there is no spatial variation of chl-a distribution (Eyasu Shumbulo, 2004). This might be due to the fact that the infestation and effect of water hyacinth may not be considered in his study.

As can be seen from (Table 12) the distribution of DO in site-1 and site-3 were 2.64±0.09 and 4.16±0.07 mg/L respectively which is less than the recommended value by WHO. According to WHO, the amount of oxygen in water above 5 mg/L is recommended and below 3 mg/L is considered as stress condition. But in site-2 and site-4, 6.74±0.01 and 6.59±0.04 mg/L respectively were observed. This result is also has similar trend to other area studies (Jafari, 2010; Mirogna, 2005 and Osumo, 2001). Charles and Dukes (2006) reported that the reduction of Dissolved oxygen occurred due to light inhibition effect of water hyacinth on phytoplanktons which are the main harvesters of oxygen in the lakes through the process of photosynthesis, However this reduction in DO may not be due the effect of water hyacinth only but also the amount of organic carbon; pH of water; temperature, depth and turbulence of water and other factors that determine the availability of Dissolved Oxygen (Delfino and Lee, 1971). The amount of organic carbon however results from rapid carbon sequestration. Plant like water hyacinth which has rapid growth rate could contribute to rapid accumulation of organic carbon in their tissue in water Osumo (2001). This organic carbon may be exposed to decomposition that utilizes oxygen. As a result of this oxygen depletion occurs. Temperature also plays key role in availability of oxygen. According to thumb rule warmer water tends to loss oxygen rapidly than cold water (Eugene, 2013). In the current study above 6 mg/L of oxygen was recorded at a temperature of 24 oC in non-infested sites but below 3 mg/L of oxygen was measured at about 28 oC in infested sites (Table 10).

TDS measurement shows less value in infested site than non-infested site which is 963.86±0.86 and 896±0.74 in site 1 and 3 whereas 533.91±0.37 and 539.73±0.81 mg/L in site 2 and 4 respectively(Table 10). This result quantitatively deviates from Ndimele (2012) which is 92 mg/L and 5460 mg/L in infested lakes and non-infested lakes respectively. This because he made his study on separate lakes which could have different physicochemical properties and the study also took eight months from January to August which again possible to measure wider range of values due to seasonal variation. Concerning pH there were slight variation observed which lies between pH of 8.5-8.65 but other studies in other countries showed that in water hyacinth infested sites, around pH 7 is recorded (Mirogna et al., 2012, Tellez, 2008)).This reduction in pH in water hyacinth infested site reasoned out by Osumo (2001). According to him, Water hyacinth has rapid growth rate and which result in increase in mass. As the mass increase, some parts of the plant material sink down and decomposed by the action bacteria releasing CO2. This gas easily mixed up with water and increases the acidity of water The salinity measurement showed relatively lower value in site-1(Table 12) which is 0.83±0.02 mg/L but in the remaining sites the measured value lies between 0.94-0.96 mg/L. This finding is also supported by Chowdhury and Ahmed (2012). For instance in lower salinity recorded site (1), the total number of water hyacinth was 75 individual (Table 12) but at site-3 which has 0.94mg/l (Table 12) the number of individuals reduced to 37. This result seems to agree with other studies. For example Jack (2005) stated that water hyacinth growth will be retarded at salinity 9ppt. On the other hand another study showed that water hyacinth has ability to tolerate and with draw some salt from water and accumulate in cell sap than other macrophytes (Elizabeth and Giussepe, 2000). Concerning conductivity, slight variation was observed, The conductivity of water in the study sites were found to be 874.0±0.51 µS/cm and 883.0±0.44 µs/cm in site-1 and 3 while 944.26±0.49 µs/cm and 958.66±1.27 µs/cm in site-2 and 4 (Table12).The current result has similar trend in terms of distribution with Ndmele (2012). TDS, salinity and conductivity are highly related parameters. In the current study in infested sites these values were lower where as in non-infested sites high values of turbidity, salinity and conductivity obtained. This trend inter relationship is stated by Eugene (2007).

Finally the TSS measurement shows that in site-1 and 3, 235.87±1.25 and 294.31±0.61 mg/L, respectively while in site-2 and 4, 373.20±0.53 and 411.25±1.24 mg/L, respectively (Table 12).This is most likely due to less number of phytoplanktons and their predators in infested sites which major contributors of TSS value in water. But in in nutrient rich area and non-infested sites, TSS seems to be higher. The recent finding is structurally has similar trend with previously results (Ababu Teklemariam and Bernd, 2004).

Pearson‟s correlation (0.01 and 0.05 significant levels) between physicochemical features of water in the study sites and occurrence of E. crassipes (Appendix 1) showed that except for salinity which has weaker negative correlation of (r =0.324, p=0.012) at two-tailed 0.05 significant level, TDS, Chl-a, Conductivity, DO, TSS and Turbidity have strong negative correlation at two-tailed 0.01 significant level. Furthermore, salinity seems to have weaker correlation with other water quality parameters with the exception of TDS. This may be due to that TDS has less variation throughout the study sites (Appendix-8). The ANOVA test using SPSS version 17 showed that there is significant variation of the water quality parameters between groups at 0.05 significant levels. But other finding showed that there is no relationship between water hyacinth infestation and water quality parameters (Zelalem Wondie, 2013). In most studies the distribution of physic chemical water parameters across the lakes has less significant variation (Erne, 2013; Eyasu Shumbulo, 2004). However other studies indicated that there is variation between those parameters with respect to water hyacinth infested sites and non-infested sites (Ndmele, 2012; Osumo, 2001).

Table 13 ANOVA result of water physicochemical parameters.

Sum of Squares df Mean Square F Sig.

1Turb Between Groups 169051.180 3 56350.393 21936.702 .003

Within Groups 143.851 56 2.569

Total 169195.031 59 chlA Between Groups 324528.404 3 108176.135 17517.683 .011

Within Groups 345.814 56 6.175

Total 324874.219 59

DO Between Groups 214.617 3 71.539 1166.550 .012

Within Groups 3.434 56 .061

Total 218.052 59

TDS Between Groups 2355058.874 3 785019.625 100188.778 .041

Within Groups 438.783 56 7.835

Total 2355497.656 59

PH Between Groups 0.141 3 0.047 63.742 0.048

Within Groups 0.041 56 0.001

Total 0.182 59

SAL Between Groups 0.157 3 .052 20.068 0.043

Within Groups 0.146 56 .003

Total 0.303 59

Cond Between Groups 82024.717 3 27341.572 3110.363 0.032

Within Groups 492.267 56 8.790

Total 82516.983 59

TSS Between Groups 278927.350 3 92975.783 6761.025 0.002

Within Groups 770.097 56 13.752

Total 279697.447 59

1Turb=turbidity, ChlA=Chlorophyl A ,DOx= Dissolved Oxygen, TDS= Total Dissolved Solids, SAL=Salinity, Cond=Conductivity, TSS= Total Suspended Solids Note: The ANOVA is computed at O.O5 significant level

The discrimination measures with two dimension(figure 20) shows that water hyacinth has more closer relation to DO, TDS, Turbidity, Chl-a and TSS than other macrophytes. But conductivity, pH and salinity seem that have not discriminated with the plant distribution. This implies that water hyacinth affect the magnitude of those parameters much more than other plants do.

Figure 15 Multiple correspondence analyses with two dimensions

Accoridng to this analysis, parameters which indicated by closer axisesor with narrow angle to the descriminator axis (the alien plant) were more affected than the other axis. For instance water quality parameters like TDS, DO, Turbidity, TSS and Chl-a are closer to the axis of E. crassipes than other macrophytes. This also indicated by Toft, (2000) that the distribution of these parameters is reduced in water hyacinth infested sites and eleveted in other macrophytes growing areas. Conductivity(cond), pH and salinityare far apart from water hyacinth and other macrophytes macrophytes which mean less relation with macrophytes distribution. Generaly conuctivity and salinity higly related and their distribution is expressed interms of the available

48 nutriens. Furthermore the discrimination is also expressed in terms of the length of the axis for instance TSS and Chl-a have relatively longer axis than others meaning they have direct relation with the discriminator. For instance change in TSS affect Turbidity and change in chl-a afects DO since oxygen is derived from chlorophyll.

5. CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusions

As indicated in the current study, water hyacinth (E. crassipes) greatly affects the floristic composition, abundance and diversity of the wetland ecosystem. The impact of E. crassipes on the abundance and distribution of macrophytes showed that the alien plant negatively affect the abundance, of macrophytes by 20% reduction. It changes the plant community in to monotypic by affecting even distribution. The study also showed that some macrophytes from Poaceae and Cyperaceae family have the ability to co-exist with the alien plant and control its spreading. This may be due to their growth habit and resistant to allelopathic impact.

The study also showed that the plant has an effect on phytoplankton distribution and abundance. Most Cyanophyceae, Bacillariophyceae and few Chlorophyceae have been observed to be associated with water hyacinth whereas most Chlorophycae were excluded from the niche. The study also showed that some nuisance phytoplanktons were observed less frequently in the E. crassipes infested site.

Concerning the water Bio physicochemical properties, the alien plant affects some of the water parameters significantly. The Pearson‟s correlation analysis showed that the alien plant has negative correlation with turbidity, chl-a, DO, salinity, conductivity and TSS whereas TDS and pH showed positive correlation at 0.01 and 0.05 (2-tailed) significant level. Multiple correspondence analysis of discrimination measure showed that water hyacinth discriminates TDS, DO, TSS and turbidity than other macrophytes do. The pH, conductivity and salinity of water are not discriminated by the alien plant. The Pearson‟s correlation also showed that water hyacinth has weaker negative correlation with salinity and pH.

In general, the impact of water hyacinth clearly manifested on the wetland ecosystem and can have role in altering the dynamics, the composition and the interaction of the ecosystem and ecosystem services.

5.2 Recommendations

As mentioned repeatedly the wetland ecosystems are not studied very well and their ecological advantage is underestimated by individual people and organizations at different levels. Based on the current research finding the following recommendations are forwarded.

 Mobilization of experts of the area and other concerned bodies towards establishment of strong policy for the protection and conservation of wetland ecosystem  Increase and Improve local people involvement in wetland protection and conservation  Training the local people to be alert on observing and protecting the wetland ecosystem from invasion with adequate techniques. Create information gathering and exchange systems between kebeles.  The impact of water hyacinth on other component of the ecosystem like zooplankton and nutrient dynamic has to be studied so as to study the profile and the ecological balance of the ecosystem.  Other component of the plant like phytochemistry, allelophatic impact on zooplankton, phytoplankton and fish has to be studied in a wider scale.  To predict the fate of the wetland ecosystem, the cumulative effect of water hyacinth cost benefit analyses should be carried out using environmental impact assessment tools.  The spreading of the water hyacinth has to be checked regularly and halted before it cause irreversible distraction on the ecosystem

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7. APPENDICES Appendix 1 Water Biophysicochemical correlation with water hyacinth

Correlations

ecras Turb chlA DO TDS PH Sal Cond TSS Pearson’s's rho ecras Correlation Coefficient 1.000 -.783** -.856** -.845** .876** .747** -.324* -.854** -.806**

Sig. (2-tailed) . .000 .000 .000 .000 .000 .012 .000 .000 N 60 60 60 60 60 60 60 60 60 Turb Correlation Coefficient -.783** 1.000 .824** .678** -.665** -.544** .367** .836** .835** Sig. (2-tailed) .000 . .000 .000 .000 .000 .004 .000 .000 N 60 60 60 60 60 60 60 60 60 chlA Correlation Coefficient -.856** .824** 1.000 .778** -.754** -.629** .266* .907** .889** Sig. (2-tailed) .000 .000 . .000 .000 .000 .040 .000 .000 N 60 60 60 60 60 60 60 60 60 DO Correlation Coefficient -.845** .678** .778** 1.000 -.890** -.663** .426** .746** .717** Sig. (2-tailed) .000 .000 .000 . .000 .000 .001 .000 .000 N 60 60 60 60 60 60 60 60 60 TDS Correlation Coefficient .876** -.665** -.754** -.890** 1.000 .670** -.442** -.752** -.747** Sig. (2-tailed) .000 .000 .000 .000 . .000 .000 .000 .000 N 60 60 60 60 60 60 60 60 60 PH Correlation Coefficient .747** -.544** -.629** -.663** .670** 1.000 -.368** -.682** -.686** Sig. (2-tailed) .000 .000 .000 .000 .000 . .004 .000 .000 N 60 60 60 60 60 60 60 60 60 Sal Correlation Coefficient -.324* .367** .266* .426** -.442** -.368** 1.000 .392** .424** Sig. (2-tailed) .012 .004 .040 .001 .000 .004 . .002 .001 N 60 60 60 60 60 60 60 60 60 Cond Correlation Coefficient -.854** .836** .907** .746** -.752** -.682** .392** 1.000 .934** Sig. (2-tailed) .000 .000 .000 .000 .000 .000 .002 . .000 N 60 60 60 60 60 60 60 60 60 TSS Correlation Coefficient -.806** .835** .889** .717** -.747** -.686** .424** .934** 1.000 Sig. (2-tailed) .000 .000 .000 .000 .000 .000 .001 .000 . N 60 60 60 60 60 60 60 60 60 **. Correlation is significant at the 0.01 level (2-tailed). *. Correlation is significant at the 0.05 level (2-tailed).

Appendix 2 Descriptive statistics some water quality parameters with respect to water hyacinth infestation in site-1

Descriptive Statistics

N Minimum Maximum Mean Std. Deviation

Site-1 Statistic Statistic Statistic Statistic Std. Error Statistic

Turb 15 20.30 24.20 22.3 .32 1.2 chlA 15 101.40 109.70 105.9 .72 2.8

DO 15 2.11 3.34 2.6 .09 .36

TDS 15 531.10 536.50 533.9 .37 1.5

PH 15 8.58 8.67 8.6 .01 .03

Sal 15 .72 .99 .83 .02 .09

Cond 15 871.00 876.00 874.0 .51 2.0

TSS 15 230.10 245.70 235.8 1.2 4.7

Valid N (listwise) 15

Appendix 3Descriptive statistic of some water quality parameters with respect to water hyacinth infestation in site-

Descriptive Statistics

N Minimum Maximum Mean Std. Deviation

Site-3 Statistic Statistic Statistic Statistic Std. Error Statistic

Turb 15 21.10 26.80 22.4 0.5 1.84 chlA 15 100.90 112.50 110.5 1.01 3.9

DO 15 2.20 3.40 3.2 0.07 0.3

TDS 15 535.00 545.00 539.7 0.81 3.13

PH 15 8.51 8.55 8.5 0.0 .014

Sal 15 .91 .98 .9 0.0 0.02

Cond 15 880.00 885.00 883.0 0.4 1.7

TSS 15 290.50 299.12 294.3 0.6 2.4

Valid N (listwise) 15

Appendix 4Descriptive statistic of some water quality parameters with respect to water hyacinth infestation in site-2

Descriptive Statistics

N Minimum Maximum Mean Std. Deviation

Site-2 Statistic Statistic Statistic Statistic Std. Error Statistic

Turb 15 120.60 128.51 125.7 0.5 2.3 chlA 15 241.30 245.30 243.8 0.3 1.15

DO 15 6.70 6.78 6.7 0.01 0.01

TDS 15 956.10 969.00 963.8 0.8 3.3

PH 15 8.48 8.55 8.5 0.01 0.02

Sal 15 .93 .98 .9 0.0 0.02

Cond 15 941.00 947.00 944.3 0.5 1.9

TSS 15 370.00 376.30 373.2 0.5 2.1

Valid N (listwise) 15

Appendix 5Descriptive statistic of some water quality parameters with respect to water hyacinth infestation in site-4

Descriptive Statistics

N Minimum Maximum Mean Std. Deviation

Site-4 Statistic Statistic Statistic Statistic Std. Error Statistic

Turb 15 131.10 131.50 131.3 0.03 0.1 chlA 15 264.70 266.10 265.2 0.10 0.39

DO 15 6.25 6.79 6.5 0.04 0.13

TDS 15 889.10 898.40 896.4 0.74 2.8

PH 15 8.45 8.58 8.5 0.01 0.03

Sal 15 .89 .98 .9 0.01 0.03

Cond 15 951.00 965.00 958.6 1.3 4.9

TSS 15 400.80 419.00 411.3 1.2 4.8

Valid N (listwise) 15

Appendix 6 Descriptive statistics of the total 60 plots

Descriptive Statistics

N Minimum Maximum Mean Std. Deviation

Statistic Statistic Statistic Statistic Std. Error Statistic

Turb 60 20.30 131.5 75.5 6.9 53.5 chlA 60 100.90 266.1 181.4 9.5 74.2

DO 60 2.11 6.7 4.7 .2 1.9

TDS 60 531.10 969.0 733.5 25.7 199.8

PH 60 8.45 8.6 8.5 .01 .05

Sal 60 .72 .9 .9 .01 .1

Cond 60 871.00 965.0 914.9 4.8 37.4

TSS 60 230.10 419.0 328.6 8.8 68.8

Valid N (listwise) 60

Appendix 7 Discrimination measurement index

Discrimination Measures

Dimension

Variable Weight 1 2 Mean

Cslu 10 0.29 0.30 0.29

Cynl 15 0.39 0.02 0.20

Cypl 17 0.68 0.59 0.63

Cydf 13 0.25 0.10 0.18

Cydv 10 0.88 0.11 0.10

Ecro 6 0.65 0.06 0.06

Lemn 12 0.52 0.59 0.55

Poly 10 0.68 0.60 0.64

Rhyc 6 0.16 0.28 0.22 ecras 20 0.53 0.05 0.29 schc 16 0.17 0.28 0.22 chlAa 0.78 0.02 0.40

DOa 0.55 0.03 0.29 turba 0.55 0.05 0.30

TDSa 0.5 0.04 0.28

Conda 0.97 0.44 0.70

TSSa 0.79 0.45 0.41

PHa 0.26 0.11 0.19 sala 0.24 0.86 0.16

Active Totalb 52.58 36.954 44.767 a. Supplementary variable. b. Variable weights are incorporated in the Active Total statistics.

Appendix 8 Some Water Biophysicchemicalmean values data from 60 plots

O plots turb Chl-a DO T TDS PH Sal cond TSS 1 22.64 102.8 2.55 29 534.3 8.67 0.98 876 242.67 2 23.4 105.4 3.34 28 531.9 8.66 0.78 876 235.3 3 23.8 108.3 3.12 28 532.4 8.59 0.79 871 234.1 4 22.9 107.2 2.13 29 534.1 8.61 0.84 875 232.9 5 24.2 101.9 2.22 29 534.3 8.63 0.98 876 241.9 6 23.9 102.3 2.31 29 536.5 8.63 0.99 872 245.7 7 21.7 103.6 2.43 29 531.1 8.65 0.92 871 233.4 8 20.3 106.8 2.64 29 532.5 8.62 0.84 873 238.2

Site1 9 20.9 108.7 2.68 29 533.6 8.58 0.72 876 230.1 10 21.2 109.7 2.84 29 533.8 8.67 0.74 875 230.3 11 22.6 108.5 2.88 29 535.2 8.65 0.82 874 237.2 12 22.5 107.1 2.91 29 534.1 8.63 0.73 875 230.1 13 23.1 107.9 2.97 29 536.1 8.61 0.73 871 236.6 14 22.2 101.4 2.11 29 534.5 8.62 0.8 873 235.4 15 20.5 107.9 2.55 29 534.1 8.63 0.8 876 234.2 16 128.5 244.6 6.7 26 969 8.5 0.98 946 371.4 17 121.3 242.3 6.7 26 963.8 8.53 0.93 945 370.6 18 125.1 245.3 6.73 26 959.5 8.53 0.95 942 371.6 19 120.6 243.9 6.74 26 965.7 8.54 0.94 941 374.2 20 127.4 244.2 6.73 26 964.3 8.49 0.95 941 373.2 21 127.2 241.3 6.78 26 956.1 8.48 0.96 946 374.1 22 125.8 245.2 6.72 26 964.9 8.53 0.94 946 370 23 125.4 243.2 6.74 26 967.3 8.53 0.97 945 371.6

Site 2 Site 24 126.4 243.5 6.75 26 965.6 8.49 0.97 947 372.3 25 127.2 244.2 6.74 26 961.8 8.49 0.98 946 371.4 26 123.7 243.7 6.73 26 966.4 8.55 0.97 944 374.3 27 128.1 242.4 6.74 26 959.9 8.54 0.96 944 375.5 28 127.2 244.6 6.75 26 963.1 8.48 0.96 945 375.4 29 126.5 244.3 6.76 26 964.9 8.48 0.97 943 376.1 30 126.1 245.1 6.75 26 965.7 8.49 0.97 943 376.3 31 21.9 112.1 3.3 28 540 8.54 0.94 880 293.2 32 26.8 112.4 3 28 535 8.53 0.96 881 297.4 33 21.3 101.2 2.8 29 541 8.53 0.98 881 298.5

34 22.1 111.8 3.2 28 539 8.54 0.94 883 293.41 35 22.3 112.2 3.2 28 536 8.55 0.94 885 293.62

36 25.5 110.23 3.2 28 535 8.52 0.93 885 290.5 Site 3 Site 37 25.6 110.59 3.3 28 545 8.51 0.94 885 291.3 38 21.8 111.9 3.2 28 543 8.54 0.92 882 294.3 39 21.3 112.5 3.3 28 541 8.54 0.91 884 294.1 40 21.1 112.4 3.4 28 538 8.55 0.94 884 294.01

41 21.6 112.3 3.4 28 542 8.52 0.93 883 294.21 42 21.5 112.4 3.4 28 541 8.51 0.92 882 293.32 43 21.6 112.5 3.3 28 537 8.52 0.93 884 294.41 44 21.4 100.9 2.2 29 539 8.55 0.97 885 299.12 45 21.5 112.5 3.2 28 544 8.54 0.96 881 293.27 46 131.2 265.6 6.693 26 897.2 8.53 0.97 954 400.8 47 131.1 264.9 6.65 27 889.1 8.45 0.95 951 414 48 131.3 264.7 6.25 27 898.1 8.46 0.98 965 413 49 131.2 265.2 6.46 26 898.2 8.47 0.91 963 415 50 131.4 265.1 6.56 26 897.4 8.52 0.89 962 419

51 131.3 266.1 6.41 26 896.9 8.54 0.91 959 415

4 52 131.4 264.8 6.55 26 896.8 8.51 0.89 961 416

53 131.3 264.7 6.58 26 897.4 8.49 0.94 957 411

Site 54 131.4 265.1 6.65 26 889.9 8.56 0.95 956 409 55 131.5 265.2 6.68 26 896.9 8.51 0.98 953 410 56 131.3 265.4 6.79 25 897.3 8.53 0.97 964 406 57 131.3 265.1 6.73 26 897.3 8.49 0.95 963 411 58 131.1 265.7 6.61 26 897.5 8.54 0.96 965 414 59 131.2 264.9 6.63 26 898.4 8.58 0.93 955 411 60 131.3 265.4 6.71 26 898.2 8.52 0.95 952 404

Appendix 9Some spectrophotometric reading for chlorophyll-a analyses

Photometry No. Wavelength(nm) Abs Trans(%T) Energy Note. 1 665.0 0.000 99.9 39769 2 665.0 0.011 97.5 38791 3 665.0 0.012 97.2 38705 4 665.0 0.019 95.8 38145 5 750.0 0.001 99.7 21445 6 750.0 0.009 98.0 21077 7 750.0 0.008 98.3 21131 8 750.0 0.013 97.2 20889 9 750.0 0.000 100.0 21551 10 750.0 0.008 98.1 21149 11 750.0 0.008 98.1 21151 12 750.0 0.018 95.9 20653 13 665.0 0.001 99.9 19945 14 665.0 0.011 97.5 19473 15 665.0 0.012 97.4 19445 16 665.0 0.027 94.0 18779 17 665.0 0.000 100.0 39953 18 665.0 0.014 96.9 38751 19 665.0 0.042 90.8 36285 20 665.0 0.020 95.5 38173 21 750.0 0.001 99.8 21513 22 750.0 0.008 98.2 21169 23 750.0 0.030 93.3 20103 24 750.0 0.017 96.1 20707 25 665.0 0.002 99.6 39865 26 665.0 0.010 97.7 39089 27 665.0 0.041 91.0 36417 28 665.0 0.007 98.5 39417 29 750.0 0.000 99.9 21569 30 750.0 0.009 98.0 21153

Appendix 10Somephytoplanktons found in study sites

1Dinophyceae 2Cyanophyceae 3Euglenophyceae

4Chlorophyceae 5Euglenophyceae 6Euglenophyceae

7 diatoms 8Cyanophyceae 9

10. closteridium like algae 11. chlorophyceae

13chlorephyceae 14cyanophyceae 15 Euglenophyceae

16(cyanophyceae)microcyst 17closteridium like algae(look #10)

Appendix 11Somemacrophytes from the study area

Some field activities carried out