1 Introduction

In 2021, global plastic production exceeded 390 million metric tons [1]. Inadequate waste disposal practices and the persistent nature of plastic waste pose significant environmental risks [2, 3], contributing to unprecedented threats to ecosystems, including marine habitats [4,5,6,7]. According to the National Oceanic and Atmospheric Administration (NOAA) marine debris protocol, these materials are divided into six categories: plastic, metal, glass, rubber, processed lumbar (no natural wood), and cloth or fabric [8]. Categorizing beach debris according to their dimensions, they are classified as follows: mega debris (exceeding 100 cm), macro debris (ranging from 2.5 to 100 cm), meso debris (measuring 0.5 to 2.5 cm), micro debris (no larger than 5 mm), and nano debris (smaller than 100 nm).

A plethora of studies have reported debris accumulating on the sea floor in oceanic gyres and coastal regions globally [9,10,11,12]. Quantification and spatial prevalence of marine debris have been assessed in marine beaches of the Moroccan Mediterranean coast [13], Takalar Regency, South Sulawesi [14], Armac¸a˜o dos Bu´zios, Rio de Janeiro, Brazil [15], coastline of Cádiz, Spain [16] and central California [17].

Research on beach debris is comparatively poor in India. The prevalence of beach debris has been assessed in different maritime states and Union Territories (UTs) [18], Marina Beach, Chennai [19], Mangaluru, Karnataka [20], Thondi coast, Palk Bay, Southeast coast of India [21], islands of the Andaman and Nicobar Archipelago, India [22] and Mumbai, India [23]. According to Kumar et al., the predominant source of debris information in India is derived from beach clean-up activities [19]. Beach clean-up activities in India offer valuable insights into the debris issue. However, they primarily lack a quantitative assessment of each debris type, hindering a comprehensive understanding of the scale and nature of the problem. The presence of beach debris poses a threat to marine organisms as it can lead to unintended ingestion and integration into the food chain [24,25,26,27]. Organisms facing debris ingestion are at risk of compromised survival, experiencing internal lacerations, prolonged hunger, and eventual mortality [28].

Gujarat's beaches play a pivotal role in supporting various socio-cultural activities, tourism, fishing, pilgrimage, and recreation [29, 30]. However, this multiplicity of engagements may be linked to the rising prevalence of debris in the marine environment [31,32,33]. Microplastic prevalence has been reported on sandy and muddy beaches of Gujarat [3, 34, 35]. A preliminary investigation of beach debris along a single beach (Mandvi, Gujarat) has previously identified land-based and recreational activity as a source of debris on Mandvi Beach [36]. Thus, a detailed investigation of the distribution, concentration, and composition of beach debris on the Gujarat coast is imperative to help inform future mitigation strategies. The objectives of this study were to assess (a) temporal variation in abundance of beach debris between three recreational beaches (Mandvi, Dwarka, and Veraval) of Gujarat state, India, and (b) different types of beach debris according to the NOAA protocol. This baseline information can help quantify beach debris and subsequent management and mitigation across the coastline state.

2 Materials and methods

2.1 Study area

Three recreational beaches on the Gujarat coast, viz. Mandvi (22° 23′ N, 68° 96′E), Dwarka (22° 23′ N, 68° 96′ E), and Veraval (20° 90′ N, 70° 35′ E) were selected to quantify the abundance of beach debris (Fig. 1). Mandvi Beach is known for tourism and fishing activities with a rich diversity of marine biota [36]. Dwarka serves as a notable fishing harbor and holds significant reverence in Hindu mythology, drawing over a million tourists each year. Veraval, the largest fishing harbor in Gujarat, sustains a multitude of seafood industries and processing facilities.

Fig. 1
figure 1

Map of study area representing sampling location of three recreational beaches (A) Mandvi, (B) Dwarka, and (C) Veraval of Gujarat, India

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2.2 Sample collection

Monthly sampling was conducted on three recreational beaches (Mandvi, Dwarka, and Veraval) in Gujarat from October 2021 to March 2022. Sampling was conducted at the high tide line mark where beach debris tends to accumulate following NOAA marine debris protocols [8]. Five quadrats (10 m × 10 m) were plotted randomly, 50 m apart from each other in the upper intertidal region parallel to the shoreline on each beach. GPS coordinates were recorded during the first sampling month, and care was taken to repeat the same stretch during subsequent sampling. All visible beach debris from each quadrat was collected in a labeled bag and brought to the laboratory for analysis (Figs. 2 and 3).

Fig. 2
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Photographic representation of field methodology

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Fig. 3
figure 3

Different types of beach debris collected from study sites

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2.3 Laboratory analysis

The beach debris was rinsed with tap water to eliminate any added soil. According to the NOAA protocol, debris was counted and separated into different categories [8]. The size of beach debris was categorized into meso-debris (5 mm–2.5 cm), macro-debris (2.5–100 cm), or mega-debris (> 100 cm). All the debris was categorized into nine different colors: white, black, transparent, red, blue, green, yellow, orange, and brown. Debris was dried under sunlight, and weight of each sorted item was recorded in g/m2 using a digital weighing balance (Sartorius, precision = 0.1 mg). Debris was classified into land-based and sea-based categories [21]. Debris from commercial shipping, fishing, boating, and fish market sites found on the shore is considered sea-based debris. Debris resulting from recreational activities, public littering, agricultural practices, and sewage classified as land-based waste.

2.4 Data analysis

Mean abundance of beach debris for each study site was calculated to analyze abundance of beach debris along three sampling sites. As the data followed a normal distribution, an analysis of variance (ANOVA) was conducted to analyze variation of mean abundance and mean weight between beach debris items using PAST software (4.03 version). The clean coast index (CCI) was used to evaluate the cleanliness of selected beaches. CCI is a measuring tool to classify beaches into different categories, for example, very clean, clean, moderate, dirty, and extremely dirty. Beach cleanness status can be useful to increase public awareness and policy-making for beach management [21, 37].

2.4.1 Concentration of beach debris

Beach debris concentration per quadrate (items/m2) was calculated as follows:

$$C_{i} = n_{i} /a_{i} \times b_{i}$$
(1)

In this context, the concentration (Ci) of beach debris items is computed as the count of items per square meter (m2), with ni representing the total number of beach debris items per transect. The variables ai and bi denote the length (10 m) and width (10 m) of the quadrate, respectively, while 'i' signifies the specific beach where surveys were carried out.

2.4.2 Clean coast index

CCI was used to measure the cleanness of the beach and was calculated as follows:

$$CCI = C_{i} \times K$$
(2)

where K is a constant (K = 20). To make the numerical value of the CCI comprehensible, K is a constant. On the basis of the number of debris on the coast, the beaches were classified as ‘clean’ to ‘extremely dirty’ [21] (Table 1).

Table 1 Pollution indices engaged in this study
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2.4.3 Plastic abundance index

The plastic abundance index (PAI) was calculated to measure the amount of plastics with reference to the total amount of beach debris [38, 39].

$$PAI =\frac{\frac{\sum \text{Plastic litter items}}{\text{Log}10 \sum \text{Total litter items}}}{\text{Length}(\text{m})*\text{Width}(\text{m})}\times 20$$
(3)

Using the PAI values as a reference, the study sites were categorized into five groups: low abundance, low abundance, moderate abundance, high abundance, and very high abundance (Table 1).

3 Result and discussion

3.1 Abundance in terms of debris numbers and weight

A total of 8105 pieces of beach debris were collected from three sampling sites (mean = 0.9 items/m2). The highest number of debris was collected from Mandvi (n = 3155), followed by Veraval (n = 3120) and Dwarka (n = 1830).. Figure 4 presents the heatmap distribution of debris (items/m2) at the Dwarka, Mandvi, and Veraval Beaches. A total of 28 different items of beach debris were found on Mandvi Beach, with straws being the most abundant, followed by balloons, gutkha pouches, and other debris items (Table 2).The mean abundance of different beach debris items did not vary significantly from each other in Mandvi (ANOVA, F = 1.29; P = 0.26). At Dwarka Beach, a total of 31 different items of beach debris were found, with plastic fragments being the most abundant, followed by plastic rope/small net pieces, buoys and floats, and other debris items (Table 2). Mean abundance of different beach debris items varied significantly from each other in Dwarka (ANOVA, F = 2.74; P < 0.05). At Veraval Beach, a total of 31 different types of beach debris were found, with clothing and shoes being the most abundant, followed by plastic fragments, plastic bags, and other debris items (Table 2). Mean abundance of different beach debris items did not vary significantly from each other in Veraval (ANOVA, F = 1.58; P = 0.16).

Fig. 4
figure 4

Heatmap distribution of debris in Mandvi, Dwarka and Veraval (items/m2)

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Table 2 Mean abundance and weight of different marine debris types collected from study sites
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The total estimated weight of beach debris was 32,598.31 g, with a mean of 3.62 g/m2 from three sampling sites. In case of total weight of beach debris, the maximum weight of debris was recorded from Veraval (14,380.59 g), followed by Dwarka (9910 g) and Mandvi (8307 g). Beverage bottles (glass) were the most abundant debris item by mean weight at Mandvi Beach, followed by medicine wrappers and other debris items (Table 2). Mean weight of debris items did not vary significantly among each other in Mandvi Beach (ANOVA, F = 1.58; P = 0.16). Rubber fragments were the most abundant debris item by mean weight at Dwarka Beach, followed by flip-flops and other debris items (Table 2). Mean weight of debris items did not vary significantly among each other in Dwarka Beach (ANOVA, F = 0.57; P = 0.71). Clothing and shoes were the most abundant debris items by mean weight at Veraval Beach, followed by paper, cardboard, and other debris items (Table 2). Mean weight of different debris items did not vary significantly from each other in Veraval (ANOVA, F = 0.30; P = 0.91). Mean abundance and weight of different debris items collected from different sites did not vary significantly between the sampling months (Tables S1–S3). Similarly, other studies recorded different beach debris abundance and weights to understand debris composition, which can be helpful in predicting the debris source in the environment [20, 40, 41]. For example, fishing-related plastic debris is attributed to local shipping activities on beaches [40]. Plastic debris, such as straws, food packaging, and plastic bags, can be attributed to tourism [41].

3.2 Monthly variation in debris accumulation

At Mandvi Beach, mean abundance and weight of beach debris were recorded in November and December (2021), respectively, while the minimum was recorded in January (2022). Mean abundance and weight of beach debris did not vary significantly between months (ANOVA, F = 1.31; P = 0.14) (Fig. 5). At Dwarka Beach, the highest mean abundance and weight of beach debris were recorded in March (2022) and October (2021), respectively, while the minimum was recorded in November (2021), respectively. It was found that the number and weight of beach debris did not vary significantly in Dwarka beach among different months (ANOVA, F = 1.31; P = 0.13) (Fig. 5). While, at Veraval beach, the highest mean abundance and weight of beach debris were recorded in October (2021), respectively, while the minimum was recorded in the month of February (2022), respectively. The number and weight of beach debris varied significantly in Veraval beach among different months (ANOVA, F = 2.30; P < 0.05) (Fig. 5). Temporal variation of beach debris between different months was recorded in other studies [23, 41]. The abundance of different debris items can be influenced by beach activities of different months [23]. There was a clear and systematic variation in the number and weight of the beach debris reported along three recreation beaches each month. Mandvi recorded higher debris accumulation during November and December, probably because of the tent city program in November and a favorable destination for tourism in December. The uneven distribution of beach debris along Mandvi Beach can be linked to the utilization of straws for beverages by beachgoers and the discarding of empty gutkha pouches, often left behind by visitors. Dwarka experienced higher debris accumulation in March and October, most likely due to the Holi-Dhuleti Festival (Hindu’s festival of colours) in March and an increase in devotees visiting the Shree Krishna temple due to Navaratri (a 9-day Hindu festival) in October. Veraval recorded a higher abundance of beach debris in October and March, probably due to fishing activities.

Fig. 5
figure 5

Monthly distribution in average abundance and weight of beach debris collected from study sites (a-Mandvi, b-Dwarka, c-Veraval)

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3.3 Size class and colour of debris

Size-wise classification revealed that macro-beach debris was dominant compared to meso and mega debris in all sites (Fig. 6). Macro size class comprises polythene bags (water pouches), plastic spoons, straws, cigarette packets, parts of fishing gear, bottle/container caps, and many other categories that indicate prevailing fishing, tourism, and other land-based activities in the coastal area. Many studies have reported occurance of different size classes of beach debris [19, 23, 42]. A total of 6872 macro debris items falling into 46 categories were recorded from the marine beach of Chennai [19]. It could reflect higher levels of anthropogenic activity near coastlines, leading to more intermediate-sized debris accumulation. Environmental factors like coastal currents might selectively deposit macro debris, amplifying its presence. It was found that the abundance of different-sized debris can vary according to the beach activities of the study sites [42].

Fig. 6
figure 6

a Size classification (Mega, Macro, and Meso) of beach debris collected from different study sites, and b Sources of beach debris (items/m2) distribution in the study sites

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This study recorded beach debris of nine different colours from each study site. Among them, white and transparent beach debris were found predominantly at all the study sites compared to other colours of beach debris (Supplementary Figs. 1, 2, and 3). Similarly, white-colored beach debris was found dominantly on the urban beaches of Mumbai [23]. White and transparent colours were found dominantly in the study sites, possibly due to the material used in food packaging at beach stalls being mainly transparent or white, which can be the source of such debris.

3.4 Source, clean-coast index (CCI), and coastal health status

Two major categories of sources were identified to contribute to beach debris at study sites. Among all three study sites, land-based sources (94%, 86%, and 85% in Mandvi, Dwarka, and Veraval, respectively) contributed to a major amount of debris generated (Fig. 6). Source-based analysis of beach debris suggests that land-based debris contributes to a more significant number of debris on the Gujarat coast. Similar findings have been reported on the west coast of Qatar [43] and the Thondi coast, India [21], which identified that land-based sources generated 45.3% and 62.45% of beach debris, respectively. Recreational activity on beaches and tourism might be the possible sources of plastic fragments, food wrappers, beverage bottles, bags, containers, medical trash, and other land based beach debris in the studied beaches of Gujarat. While extensive fishing activities can be possible source of fishings ropes, nets, line, buoys, and floats in the studied beaches.

Beach debris concentrations at Mandvi and Veraval beaches were 1 item/m2 with CCI values of 20, which was classified as “dirty”. Similarly, Dwarka Beach had concentrations of 0.6 items/m2 with CCI values of 12, also classified as “dirty”. The CCI identified all three beaches as dirty. Similarly, the beaches of southwestern Luzon, Philippines, and Salvador, Brazil, were also recorded as dirty beaches by Paler et al. [44] and Fernandino et al. [45], respectively. According to CCI results, Dwarka falls into the initial stage of dirty categories that can be changed from dirty to moderate by better management and regular cleaning of the beach. While Mandvi and Veraval fall into post-stage dirty categories, they can become “extremely dirty” if no policy-making or quick action is taken for beach conservation. Research on debris surveys in marine ecosystems suggests a high figure to understand fresh and accumulated litter prevalence across coastal zones, which has been reported to have a harmful effect on marine biota. The PAI values of all three sites highlighted a very high abundance of plastic compared to other beach debris (PAI > 8). Similarly, Perumal et al. found that PAI 4.37 indicates a high abundance of plastic concerning other beach debris [39]. The study uncovered that plastic debris prevailed predominantly across all the study sites, underscoring its prevalence in comparison to other forms of beach debris. This trend aligns with findings from similar studies emphasizing the dominance of plastic debris [23, 46, 47]. The prolonged resilience and widespread accessibility of plastics contribute significantly to their extensive usage in various consumer and household-related products across different countries [23]. Improper waste management leads to the eventual introduction of a substantial amount of plastic waste into the marine environment.

This study revealed that anthropogenic activities like fishing and tourism might be responsible for debris accumulation on studied beaches. Several studies have observed that coastal urbanization, sewage, tourism, fishing activities, and religious festivals are believed to play a significant role in debris concentration in the ocean [18, 19, 23, 48]. Furthermore, Barnes established a compelling correlation between debris abundance and the human population residing in coastal regions [49]. This connection implies that human-related activities significantly contribute to the accumulation of debris in marine ecosystems.

3.5 Compared with previous studies on plastic debris on beaches in India and across the globe

Comparison of marine debris (items/m2) with different studies across the world is given in Table 3. This study revealed that beach debris abundance on Gujarat beaches was lower than from beaches of other Indian states such as Maharashtra (68.8 items/m2) [23] and West Bengal (0.98 items/m2) [41]. In contrast, a higher abundance of beach debris was recorded in the beaches of Gujrat as compared to the Atlantic Ocean, Rio de Janeiro, Brazil (0.13 items/m2) [15], East China Sea, Northern Taiwan (0.15 items/m2) [50], and Bay of Bengal, Bangladesh (0.27 items/m2) [6]. Beaches with fishing activities, tourism, and improper solid waste management were more susceptible to contributing to beach litter in marine environments [20].

Table 3 Global comparison of marine debris (items/m2)
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4 Conclusion

This baseline study reports the quantitative analysis of beach debris pollution on recreational beaches of Gujarat that provides insight into the pollution status of the coastline. Beach debris was mainly derived from fishing activities and tourism. This study provides baseline data that can help create awareness of regular beach clean-ups, proper waste management, recycling, and reuse of debris materials, including plastic, in the marine environment. Future marine debris monitoring needs to be implemented to identify the impact and trends of beach debris on the Indian coast, which would allow results to be compared at local and global levels. There is also a need for a long-term study on debris prevalence to understand the effect of beach debris on human and marine biota on the Gujarat coast.

4.1 Limitations of the study

While this study offers valuable insights into beach debris pollution along the Gujarat coastline, it is important to acknowledge some limitations and considerations in the methodology. The study was conducted over a relatively short period from October 2021 to March 2022, which may not fully capture seasonal variations in debris accumulation and composition. Long-term monitoring efforts would provide a more comprehensive understanding of beach debris dynamics. Additionally, this study did not delve into the patterns of coastal currents or conduct seasonal surveys to assess their impact on marine debris accumulation. As a result, the dynamic nature of debris accumulation over time and its interaction with seasonal variations remain relatively unexplored. Moreover, all visible surface debris within each quadrat was meticulously collected, aiming to minimize the potential error associated with overlooking very small, unseen debris. Despite these limitations, this study lays the groundwork for further research and underscores the importance of addressing beach debris pollution through targeted management and conservation efforts.

4.2 Future directions and recommendation

The current study provided the preliminary understanding of beach debris acumuation in three recreational beaches of Gujarat. However, future research on beach debris pollution along the Gujarat coastline should focus. Continued monitoring and data collection are essential to understand the long-term trends and impacts of beach debris on both the marine ecosystem and human activities. This can help in identifying hotspots of debris accumulation, seasonal variations, and changes over time. Additionally, research efforts should be directed towards investigating the sources and pathways of beach debris, including contributions from land-based activities, fishing, tourism, and improper waste management practices. Understanding these factors can inform targeted interventions and policies aimed at reducing debris input into the marine environment. Furthermore, collaborative efforts involving government agencies, local communities, NGOs, and other stakeholders are crucial for implementing effective waste management strategies, promoting beach clean-up initiatives, and raising awareness about the importance of reducing, reusing, and recycling debris materials. Moreover, future studies should explore the ecological and socio-economic impacts of beach debris pollution to develop comprehensive management approaches that safeguard both marine ecosystems and coastal communities.